Lines on the screen.
I opened up an iphone 6 to look for physical damage as it had a cracked screen. all I removed were the 4 molex connectors that attach the digitizer to the back of the phone. Once I verified no other physical damage by examining under the microscope I gave my customer a quote and they chose not to repair it. The phone and all functions were working fine before I opened it but now that I reconnected the connectors it has a bunch of small blocks on the screen.