@Random Penguin well then.

The second screenshot in my post was how the photos are sorted on Pleroma (another AP social network), there the order was as uploaded.

So this means (only) Friendica shuffles the photos. Or at least Pleroma does not.

I am used to it, it happens since some time.

Can you reproduce it when you create a post?

Maybe take a photo with 1 thing in it, one with 2 things in it and a third one with 3 things in it.