Disappearing Annotations (Notes/Scribbles) on Nova Pro

I have a Nova Pro. On several occasions annotations/notes/scribbles for a file will simply randomly disappear. I had this happen for a 300 page book: one minute fine. The next minute everything had disappeared.

Is this a known bug? Is there any way to retrieve these annotations?

It is rather strange. Have you delete any document under Storage? If not, please submit this on Feedback via Settings/ Feedback on your device and our team will reply back as soon as possible.