I agree with @paulakreuzer.
I addition to that the upper ground contact in the picture is shifted, what means it was forced in one direction.
How does your screen looks like in the area where the bottom module sits? Also these kind of marks?
Yeah now that I’m opening it up again, it seems like the outline of the marks on the bottom module correspong to the borders of the metallic parts on the screen. On the screen there are also signs of the residue but much less than on the bottom module.
Could it have something to do with the phone getting hot (which it does from time to time when using it intensively or charging)?
There is a slight crack in my case extending from the camera button.
My main concern is that there is something wrong with the phone that is damaging these bottom modules and that if I get a new one it’ll break again quickly. I don’t know what to do …
Honestly, my advice is don’t worry too much: I am also now on my fourth bottom module in less than 4 years, and as I read in this forum, lots of people have these issues. Just get a replacement under warranty or if you do not have warranty anymore, buy a new bottom module and this one again comes with warranty. For me these modules last about 1 year, sometimes only half a year. It’s obvious that the modules have some serious problem, but as long as we can get (mostly) free replacements I think we can live with it So I’m 99 % sure it’s not your fault