Actually I am on creation countless Alt. Versions for several Disc IDs as they are used in more different box sets. As I want to keep the parent covers "officialy" for the childs, too, I have to do that and it's just a little bit of time to invest.

So the new Alt. Versions get the covers of the parent profile (which has allready been resized here online and isn't changed by the update anymore). But when I check the (now newly released) updates now, I get image updates. If I check them, there is absolutely no difference - neither in dimensions nor in fil size - but obviously anything has "changed". Is there any value "behind the comma", which could have a minimal variaton which caused that?

That's the first thing I am simply not able to understand. But what it makes even more difficult to understand is the fact, that this doesn't happen for all the childs of the same profile. I got 1 series ("Die Schlümpfe" ("The Smurfs")), consisting of 40+ discs with all 9 seasons. I did the same job for all discs, but only some seasons got this confusing image update, others luckily didn't.

For a season of another series, only 1 disc of 4 got this (not existing) update.

Especially in this situation I have to control every single one as it could have happened that I didn't create an Alt. Version for a disc (then I would get an update with the cover of the "original" Disc ID). But controlling and finding out that there is no (visible) change, is confusing.

a) How does this work or how could this happen?
b) Is there any change to avoid an update of replacing an image with an obviously identical one?