This appears to be quite a specific error where the sequence of events matters.
In the case where a document has been created and signed, but signed with the settings such that markups are still allowed to be added to the document after signing. Then in a different application, markups are added to the document. Specifically, markups that contain an image. Then when you open that document in Reader, the image cannot be seen. You can tell that there is a markup there, the outline shows up and you can click on it and show properties and everything but the image itself is not there.
This issue does not appear to happen in any other pdf viewer that I have tried.
Comment markup and annotate, Security digital signatures and esignatures, View PDF