HypersomniacLive: It might be related to the fact that I'm running Waterfox in Sandboxie, hence why I made the note about it.
Can you check if the covers choking/not loading are exclusively the ones hosted on GOG? I've noticed that it's not as bad in the afternoon (fewer images and a page refresh usually fixes the issues).
adaliabooks: I've just tried it again in Firefox (and Chrome) and had no issues, pictures loaded fine with only a few being a little slow but no corrupt ones or errors...
It may well be to do with time of day and busyness, perhaps GOG are up to something that is affecting their servers?
I don't think I own many games that needed me to host images for them so I'd imagine most (if not all) of the ones I got errors for are GOG hosted, but I'll try and remember to check again tomorrow and see if it happens again.
Might or might not be relevant.
GOG's servers have been acting up since the beginning of the Lunar New Year Sale. It's as if some servers are ok and some not, so MaGog sees intermittent inconsistencies. For example, she has been seeing back and forth changes in games' changelogs, at one point including the most recent update, then minutes later missing the same update, or vice versa, primarily affecting games that have had their changelog updated since the beginning of the Lunar New Year Sale (i.e. as if some servers got updated with the new info and some not). I have added code to MaGog to work around it as best I can.
These things tend to happen during sales, but this time the sale is over and gone, but the issues persist. I didn't contact GOG about it because...
I can't comment on MarkoH01's specific issue as I don't use AF's library features.