Hi guys. I need help with an iPhone 6. Mind you this is not the first iPhone 6 LCD I replaced so I'm not exactly a beginner. I did everything by the book as I replaced the cracked screen and everything seemed okay after reassembly. But after about 30 minutes , an hour tops of testing the signal dropped and I can't seem to be able to get it back. I tried disassembling everything again and looked if everything is in order and seems that everything is properly connected back. The client tried to send it back to warranty without talking to me first and they repair centre said that it MIGHT be that the motherboard got damaged while replacing the LCD but I find it difficult to believe as I have replaced and least other 20 iPhone LCDs in the past without any issue. Now of course I have to take full responsibility and I am evaluating if I should change the whole motherboard or not. If anyone could point me in the right direction and help me avoid doing that I would greatly appreciate it.

UPDATE: No..the person asked if signal problem could be because he changed the screen. As for me...I really don't know...I used plastic tools...quality spare screen. I'm asking my self now if maybe I put the wrong screw but..small update...when I do a factory reset the signal comes back for about 5 minutes in which I'm able to make phone calls after which the signal is lost again. I'm lost...can't figure out what it is. Anyone knows where exactly I'm suppose to look for damage signs? The phone was working prior to the lcd replacement, that, unfortunately I know for a fact.