mechtheist

I have this problem, my note list snippet and card views have a lot of notes with large 'X's instead of thumbnails--see ss. They are almost all whole-page save notes from 3D model pages from like thingiverse, the one in ss is the first one, before then, 9/13/20, there was no problem, after it got worse and worse until by 10/19/20, virtually all notes are doing this. The problem is almost completely confined to these type pages, or this one notebook. In thumbnail view, I'm only seeing like 10 thumbnails out of over 400 notes. Any ideas? Why can't there simply be a right-click menu item to pick the picture in a note to be its thumbnail? Thanks of any help anyone can give