We are running umbraco 7.15.1

Sudenly we started getting cache error on our logo file and it is happenning randomly. On first occaccion it caused all our website down.

Despite it is the main image of the site - the logo - it does happen only in selected random places. For example the logo displays fine on the website header but fails in an email template or schema snippet.

When it first happened we did update dll on the server and the issue seemed to have been gone but it suddeny happened again yesterday - in a totally different place - in a scheduled task in this case.

Does anybody knows why this may be happening or how to permanently stop it happening again?

This is the example of the related stacktrace:

 2020-01-01 00:02:59,398 [P20600/D2/T8] ERROR Umbraco.Core.UmbracoApplicationBase - An unhandled exception occurred
System.Exception: Exception while creating a value. ---> System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at Lucene.Net.Util.BitVector.Get(Int32 bit)
   at Lucene.Net.Index.SegmentTermDocs.Read(Int32[] docs, Int32[] freqs)
   at Lucene.Net.Search.TermScorer.NextDoc()
   at Lucene.Net.Search.ConjunctionScorer..ctor(Similarity similarity, Scorer[] scorers)
   at Lucene.Net.Search.ConjunctionScorer..ctor(Similarity similarity, ICollection scorers)
   at Lucene.Net.Search.BooleanScorer2.CountingConjunctionSumScorer(IList requiredScorers)
   at Lucene.Net.Search.BooleanScorer2.MakeCountingSumScorerSomeReq()
   at Lucene.Net.Search.BooleanScorer2.MakeCountingSumScorer()
   at Lucene.Net.Search.BooleanScorer2..ctor(Similarity similarity, Int32 minNrShouldMatch, IList required, IList prohibited, IList optional)
   at Lucene.Net.Search.BooleanQuery.BooleanWeight.Scorer(IndexReader reader, Boolean scoreDocsInOrder, Boolean topScorer)
   at Lucene.Net.Search.BooleanQuery.BooleanWeight.Scorer(IndexReader reader, Boolean scoreDocsInOrder, Boolean topScorer)
   at Lucene.Net.Search.IndexSearcher.Search(Weight weight, Filter filter, Collector collector)
   at Lucene.Net.Search.Searcher.Search(Query query, Collector results)
   at Examine.LuceneEngine.SearchResults.DoSearch(Query query, IEnumerable`1 sortField, Int32 maxResults) in C:\projects\examine-qvx04\src\Examine\LuceneEngine\SearchResults.cs:line 110
   at Examine.LuceneEngine.Providers.BaseLuceneSearcher.Search(ISearchCriteria searchParams, Int32 maxResults) in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Providers\BaseLuceneSearcher.cs:line 182
   at Examine.LuceneEngine.Providers.BaseLuceneSearcher.Search(ISearchCriteria searchParams) in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Providers\BaseLuceneSearcher.cs:line 163
   at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetUmbracoMediaCacheValues(Int32 id)
   at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.<>c__DisplayClass38_0.<GetCacheValues>b__0()
   at Umbraco.Core.Cache.DictionaryCacheProviderBase.<>c__DisplayClass10_0.<GetSafeLazy>b__0()
   --- End of inner exception stack trace ---
   at Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, Func`1 getCacheItem, Nullable`1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, CacheDependency dependency)
   at Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, Func`1 getCacheItem, Nullable`1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, String[] dependentFiles)
   at Umbraco.Core.Cache.DeepCloneRuntimeCacheProvider.GetCacheItem(String cacheKey, Func`1 getCacheItem, Nullable`1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, String[] dependentFiles)
   at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetCacheValues(Int32 id, Func`2 func)
   at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetUmbracoMedia(Int32 id)
   at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetById(UmbracoContext umbracoContext, Boolean preview, Int32 nodeId)
   at Umbraco.Web.PublishedCache.ContextualPublishedCache`1.GetById(Boolean preview, Int32 contentId)
   at Umbraco.Web.PropertyEditors.ValueConverters.LegacyMediaPickerPropertyConverter.ConvertSourceToObject(PublishedPropertyType propertyType, Object source, Boolean preview)
   at Umbraco.Web.PublishedCache.XmlPublishedCache.XmlPublishedProperty.get_Value()
   at Umbraco.Web.PublishedPropertyExtension.GetValue[T](IPublishedProperty property, Boolean withDefaultValue, T defaultValue)
   at Umbraco.Web.PublishedContentExtensions.GetPropertyValue[T](IPublishedContent content, String alias, Boolean recurse, Boolean withDefaultValue, T defaultValue)
   at Umbraco.Web.PublishedContentExtensions.GetPropertyValue[T](IPublishedContent content, String alias)
   at MySite.PublishedModels.Settings.get_Logo()
   at MySite.PublishedModels.AppSettings.ContentSettings.get_Logo()
   at ASP._Page_Views_Master_cshtml.Execute() in D:\Inetpub\vhosts\MySite.com\httpdocs\Views\Master.cshtml:line 36
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.WebPages.WebPageBase.<>c__DisplayClass40_0.<RenderPageCore>b__0(TextWriter writer)
   at System.Web.WebPages.HelperResult.WriteTo(TextWriter writer)
   at System.Web.WebPages.WebPageBase.Write(HelperResult result)
   at System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action`1 body)
   at System.Web.WebPages.WebPageBase.PopContext()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance)
   at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer)
   at Umbraco.Core.Profiling.ProfilingView.Render(ViewContext viewContext, TextWriter writer)
   at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_6.<BeginInvokeAction>b__4()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_1.<BeginInvokeAction>b__1(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult)
   at System.Web.Mvc.Controller.<>c.<BeginExecuteCore>b__152_1(IAsyncResult asyncResult, ExecuteCoreState innerState)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
   at System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult)
   at System.Web.Mvc.Controller.<>c.<BeginExecute>b__151_2(IAsyncResult asyncResult, Controller controller)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
   at System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult)
   at System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult)
   at System.Web.Mvc.MvcHandler.<>c.<BeginProcessRequest>b__20_1(IAsyncResult asyncResult, ProcessRequestState innerState)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
   at System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult)
   at System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

And another example from yesterday:

 2020-01-05 16:01:17,255 [P20288/D2/T55] ERROR MySite.TaskScheduler.Controllers.ReviewApiController -  ** EX ** ***** Review request has failed sending for booking 8XGS1T
System.Exception: Exception while creating a value. ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at Lucene.Net.Index.SegmentReader.Norm.Clone()
   at Lucene.Net.Index.SegmentReader.ReopenSegment(SegmentInfo si, Boolean doClone, Boolean openReadOnly)
   at Lucene.Net.Index.SegmentReader.Clone(Boolean openReadOnly)
   at Lucene.Net.Index.IndexWriter.ReaderPool.GetReadOnlyClone(SegmentInfo info, Boolean doOpenStores, Int32 termInfosIndexDivisor)
   at Lucene.Net.Index.DirectoryReader..ctor(IndexWriter writer, SegmentInfos infos, Int32 termInfosIndexDivisor)
   at Lucene.Net.Index.IndexWriter.GetReader(Int32 termInfosIndexDivisor)
   at Lucene.Net.Index.IndexWriter.GetReader()
   at Lucene.Net.Index.DirectoryReader.DoReopenFromWriter(Boolean openReadOnly, IndexCommit commit)
   at Lucene.Net.Index.DirectoryReader.DoReopen(Boolean openReadOnly, IndexCommit commit)
   at Lucene.Net.Index.DirectoryReader.Reopen()
   at Examine.LuceneEngine.Providers.LuceneSearcher.ReaderReopener.MaybeReopen() in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Providers\LuceneSearcher.cs:line 610
   at Examine.LuceneEngine.Providers.LuceneSearcher.ReaderReopener.ScheduleReopen() in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Providers\LuceneSearcher.cs:line 441
   at Examine.LuceneEngine.Providers.LuceneSearcher.ValidateSearcher() in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Providers\LuceneSearcher.cs:line 368
   at Examine.LuceneEngine.Providers.LuceneSearcher.GetSearchFields() in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Providers\LuceneSearcher.cs:line 245
   at UmbracoExamine.UmbracoExamineSearcher.GetSearchFields()
   at Examine.LuceneEngine.Providers.BaseLuceneSearcher.CreateSearchCriteria(String type, BooleanOperation defaultOperation) in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Providers\BaseLuceneSearcher.cs:line 117
   at UmbracoExamine.UmbracoExamineSearcher.CreateSearchCriteria(String type, BooleanOperation defaultOperation)
   at Examine.LuceneEngine.Providers.BaseLuceneSearcher.CreateSearchCriteria(String type) in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Providers\BaseLuceneSearcher.cs:line 273
   at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetUmbracoMediaCacheValues(Int32 id)
   at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.<>c__DisplayClass38_0.<GetCacheValues>b__0()
   at Umbraco.Core.Cache.DictionaryCacheProviderBase.<>c__DisplayClass10_0.<GetSafeLazy>b__0()
   --- End of inner exception stack trace ---
   at Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, Func`1 getCacheItem, Nullable`1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, CacheDependency dependency)
   at Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, Func`1 getCacheItem, Nullable`1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, String[] dependentFiles)
   at Umbraco.Core.Cache.DeepCloneRuntimeCacheProvider.GetCacheItem(String cacheKey, Func`1 getCacheItem, Nullable`1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, String[] dependentFiles)
   at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetCacheValues(Int32 id, Func`2 func)
   at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetUmbracoMedia(Int32 id)
   at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetById(UmbracoContext umbracoContext, Boolean preview, Int32 nodeId)
   at Umbraco.Web.PublishedCache.ContextualPublishedCache`1.GetById(Boolean preview, Int32 contentId)
   at Umbraco.Web.PropertyEditors.ValueConverters.LegacyMediaPickerPropertyConverter.ConvertSourceToObject(PublishedPropertyType propertyType, Object source, Boolean preview)
   at Umbraco.Web.PublishedCache.XmlPublishedCache.XmlPublishedProperty.get_Value()
   at Umbraco.Web.PublishedPropertyExtension.GetValue[T](IPublishedProperty property, Boolean withDefaultValue, T defaultValue)
   at Umbraco.Web.PublishedContentExtensions.GetPropertyValue[T](IPublishedContent content, String alias, Boolean recurse, Boolean withDefaultValue, T defaultValue)
   at Umbraco.Web.PublishedContentExtensions.GetPropertyValue[T](IPublishedContent content, String alias)
   at MySite.PublishedModels.Settings.get_Logo()
   at MySite.PublishedModels.AppSettings.ContentSettings.get_Logo()
   at MySite.Umbraco.Settings.Branding.get_Logo()
   at CompiledRazorTemplates.Dynamic.RazorEngine_e33f29a961664c7c858a7440f88c8a18.Execute()
   at RazorEngine.Templating.TemplateBase.RazorEngine.Templating.ITemplate.Run(ExecuteContext context, TextWriter reader)
   at RazorEngine.Templating.TemplateService.Run(ITemplate template, DynamicViewBag viewBag)
   at RazorEngine.Templating.TemplateService.Parse(String razorTemplate, Object model, DynamicViewBag viewBag, String cacheName)
   at MySite.Services.Notification.Emailer`1..ctor(T model, String subject, String messageTemplate, Dictionary`2 replacements, String pathToEmailTemplates)
   at MySite.TaskScheduler.Controllers.ReviewApiController.<SendReviewRequest>d__9.MoveNext()