My display seems to fail randomly, even after changing LCD. What could it be?

[AC Question]

So here's my issue. Yesterday, my phone started to give me a while screen full of dead pixels (pinkish color) randomly. I would turn off the phone, turn it back on and after 2-3 minutes it would crash again. Last year I dropped it and cracked the screen, so to me it was related to that. The phone works fine other than that (music plays when display fails. I did wipe it completely and reinstalled Kit Kat, it solved the issue temporarily but after 30 minutes it started again.

Today I decided to go check out a phone repair shop and ended getting my phone fixed by them. What this consisted of is a replacing the display and plastic frame. I picked up the phone and everything was perfect, new screen and display which looks and feels like new.

Now it's been about 5 hours and the phone started acting strange again. Now it's a lot less worse than before, but I still get the full screen of dead pixels. The display will go on and off (I guess it's trying to reinitialize or something) but always fails. So I end up rebooting the phone for it to work again.

The 2 times it happened after getting the phone fixed it was when I put it in my pocket to go from my work to my car, and then from my car to my home. So I don't know if it has anything to do with being in my pocket, that's why I came here.

So could anyone could shed some light on my issue here? Is my phone already dying? It's only been 13 months I'd hate to have spent for a new display for basically nothing.

Thank you!

 

[Rukbat]

When you dropped it, the motherboard probably cracked. The crack gets worse as time goes on.

Will it pay to replace the motherboard? If it's a $700 phone and you can get a new motherboard for $150, sure. If it's a $150 phone and a new motherboard is $100, probably not.