Touch screen quits working after 1 week repeatedly.

I have a phone I have fixed we put a new screen on it and it stopped working after a week. So my employee reset the flex cables and it worked. The next week the guy comes back and it has quit working after 1 week again. I replace the screen this time and it works. Then he comes back after another week. I clean and inspect the connections put another screen on and inspect the screen to make sure all the grounding tape is on right it works. Sure enough the next week he comes back. This time I just reset the phone and it works for him. I am trying to figure out what the long term fix could be. To clarify the customer says this phone continues working for about a week each time.