If you turn off the Amazon covers, at least it won't get any worse...? (And that doesn't erase the data of which Amazon cover you would have had, I was worried about that for awhile, but it still shows as selected in the cover change dialog, just not anywhere else.) I find going in and fixing Amazon covers relaxing, but then I still have 4000 unfixed ones, so not that relaxing.

I don't think there's any way to get a warning if one is about to change (amazon just...does it, silently) but you can go into your stats/memes and get a catalog filter of all your books with Amazon covers.

Also, the mobile app has a built-in way to photograph & correct covers that makes it way easier to add not-cheating real ones than it used to be.