Rear Camera "sometimes" not working after battery replacement

Hi all!

After I replaced the battery of my iPhone 6 I had issues with the rear facing camera (and flash) not working.

Using this forum I found that it could be that the camera got damaged while replacing some parts, therefore I ordered a new camera, replaced it and it worked, great! (Or so I thought).

After using the phone now for two days I found that the camera sometimes works but more often it fails, even weirder: sometimes I am able to use the flash and not the camera and sometimes I'm not able to use either of those...

I am really puzzled by this issue right now, how can it be that the camera randomly switches between working, only using the flash and not working at all?

I was wondering if it was heat related but the phone doesn't seem to be any hotter than before the battery (or camera) replacement. Furthermore the issue does not seem to be related to heat since I am sometimes able to use the camera then the phone is a little hotter and sometimes not able to use the camera when the phone has been idling for a while and therefore not hot at all...

I also tried the DFU reset but that did not change anything.