For anyone else coming across this post - we had a similar issue and it worked out to be when pasting nested content from another nested content block.

To resolve this, we have to past the content, then expand every nested content block to show the data that was pasted in. If we hit save and publish then it all works properly.

For anyone running into this, it looks like a bug in Umbraco when using the copy and paste funtion for content in a nested list.

I found the easiest way to fix this is to:

1. Create a copy of the page (right click on ... on the page in the content tree -> select "copy"). Dont select "relate to original".
2. Delete the original page (and rename your copy to the original page name)
3. Save and publish

The act of creating a copy of that page seems to fix the guids in the nested list. The new copy of the page works fine.

We are also getting this; fortunately it's in a development environment where I'm testing, but the solutions above won't work for us as it's an automatic process that loads around 400 documents from XML.

The process sets accordion data into Nested Content like this:

        var items = new List<Dictionary<string, object>>();
        items.Add(new Dictionary<string, object>() {
                {
                    "ncContentTypeAlias",
                    "accordion"
                },
                {
                    "headerText",
                    headerText.ReplaceMany(_htmlReplacments)
                },
                {
                    "accordionContent",
                    cleanAccordionContent
                }
        });
        umbracoNode.SetValue(fieldname, JsonConvert.SerializeObject(items));

This used to automatically set the key value in the UmbracoPropertyData table, but now it seems that it sets a blank Guid instead - this then can't be parsed or loaded on the front end.

I'm going to try manually inserting the key but this seems like a pretty serious bug - I will raise it with support!

It appears I can "fix" it by just adding the key to the object myself - I might need to revisit this if they fix the bug! (Also I'm making the dangerous assumption here that the Guid I generate isn't going to be used elsewhere, although I think that's fairly safe).

Unfortunately this is only one update and there are lots, so deleting/adding new documents would generate a massive overhead - it would only be on the back office server, but it would play havoc with the process I think.

Thanks for the thought though! :)

        items.Add(new Dictionary<string, object>() {
                {
                    "key", 
                    $"{Guid.NewGuid()}"
                },
                {
                    "ncContentTypeAlias",
                    "accordion"
                },
                {
                    "headerText",
                    headerText.ReplaceMany(_htmlReplacments)
                },
                {
                    "accordionContent",
                    cleanAccordionContent
                }
        });

Getting the same error in 8.11.1..

Have some nested content inside a nested content that trows a "Empty guid" after I copied.

When I open a Nested content. It opens all..

If I copy and then delete each nested content and then insert it again then they works... ?

Tried to open all nested and save.. Didn't do anything..

It's on the root node, it´s a lot of sub pages that needs to be copied.. :p

I will give it a try

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