Weird Screen Fading and bootloop

Hey all again, I was write my problem i guess i solved it nearly but i have still problems on my iPhone 5

When heats up, not so much between 30-33c, everytime i open something screen slowly fading with annoying colors and going to bootloop. This is started after u2 replacement. its working fine except this reboots. i have 2 questions.

1.Is there possible NAND Corrupted?

2.It can caused by bad u2 ?