Ghosting after screen replacement

I changed the display of my phone and everything was fine, only when the phone was in ist's protective case it took a few hours and it started ghosting...

I had it in my pocket for hours without case, never a problem. I tried two different Cases, it always ended switching the phone off and on again.

Whenever the ghosting(touches registered, where I didn't touch) starts I have to restart the phone and everything is back to normal.

Now I realized I lost a little part: the little golden hook on the lower third of the phones side.

Could that be a problem? If so, what is the name of that piece and where can I get it?