Camera displays/flashes partly purple and sometimes crashes

Hi everyone,

I recently bought a used iPhone 4s. Now I have the following problem: Sometimes when I open the camera app, the display flashes partly purple/pink then turns very dark and sometimes the app even crashes. I did some research and it sounded very similar to the problem some iPhone 5 users experienced. Just to make this clear it is not just the 'purple flare', it is completely purple/pink boxes covering most of the screen.

But then, most of the times the camera is working just fine.

I also noticed that when I put the phone down or the vibration alarm goes off it sounds like something is loose in the camera region. Could it be a physical problem even though the camera still seems to work (mostly) fine?

Any advice or ideas are very much appreciated! Thank you!