I am a professional phone repairer from down under and, as everyone else, I too experienced the white vertical lines or the white squares issues.
I have done some research and experimenting, and now I deal with the problem effectively.
This solution is only for lines or squares on the LCD. It's a solution intended for professional repairers; many amateur repairers do damage to the LCD while attempting the repair.
Here come some considerations valid for most of the cases:
1 - The problem doesn't come from a defective screen.
2 - This problem is typically experienced with several screens on the same phone.
3 - The problem arises from static electricity.
4 - The problem doesn't occur often with original screens.
5 - The problem is much more likely to happen with low or deteriorated batteries.
So when I encounter the problem in a particular phone, I follow this sequence:
- Unplug the screen
- Unplug the battery
- Wait 30 seconds
- Brush screen contacts
- Replug the screen and make sure connectors sit properly
- Replug battery
- Test again
I follow this sequence 2 - 3 times at least.
If problem remains unsolved:
- Try a new screen (keep previous screen; it will be good for the next repair)
- Follow previous process again
If problem still remains unresolved and the battery is low or deteriorated (soft or inflated), charge or replace the battery and test again.
- If problem still persists, leave the LCD on the phone and explain to the costumer that the problem will typically disappear after 1-3 days or after recharge. If not, reimburse (hasn't happen to me so far).
Hope this helps someone else.