Comment by Nonexistent Author when Opening Presentation from SharePoint File

We have an Azure Function that pulls PPTX files from SharePoint Online to generate the slide images in a document library. We are having an issue with certain decks that were migrated from SharePoint 2019 to SharePoint Online.

It appears that comments made in 2019 are migrated successfully to Online, but when processed in Aspose.Slides, we get an exception:
Object reference not set to an instance of an object.

And sometimes, we are able to tease out the following inner exception:

Comment by nonexistent author. AuthorId: <>

We’ve had to strip comments and start anew in many places. However, when creating NEW comments entirely in SharePoint Online, SOME comments still error with that same message. This error message occurs in other SharePoint tenants, and is not isolated to a specific user making a comment or including a mention in the comment.

The largest frustration is that we do not even CARE about the comments - but there is no way to start the function before it errors on line:

using (Aspose.Slides.Presentation pres = new Aspose.Slides.Presentation(memory))
(The memory value is read from the SharePoint file)

If we remove certain comments, the error goes away. However, we have to go comment by comment to find the “BAD” comment(s), and we honestly don’t want to remove them.

I have tested this using the free trial of the latest Aspose.Slides for .NET, as well as our current licensed version, but the error still appears.


Can you please share a sample PPTX document that causes the described issue?