After a weekend of testing, here is what I think I know (might not be 100% accurate because the deletions appear to be random each time, so it could just be chance that a particular artist’s image didn’t happen during my testing, but may happen another time):
- The deletions affect artists with ONLY Korean and Japanese characters in the artist name and album artist name. It doesn’t seem to happen with a mixture of Korean/Japanese characters + English. It doesn’t seem to happen with names that include any punctuation, Russian letters or of course English.
- Artist name — and ---- seem to be affected, although I only got it to trigger once, but like I said above that could just be chance.
- The deletions only happen when adding/changing artist thumbnail to an affected artist. It’s random what other artist loses their photo in this moment. But fortunately now I’ve finished setting up my library, I shouldn’t experience these deletions again as it takes adding/changing a thumbnail to trigger the deletions.
- Backing up the “cached_thumbnails” folder and then after a deletion pasting the missing images back into the folder works, and the images are now visible again in the app.
Hope that helps anyone else who may have this problem!