Cubot x6 crash and freeze with white screen?

[AC Question]

OK so i have this phone 2 years and it worked perfectly, and it started freezing and crashing with white screen without any reason, sometime it crash after boot sometime he crash after few hours of using. When it crash it stay frozen about 10-20 minutes and then reboot, i reinstall both stock and custom roms, but problem is still there. Pls help me cause i love that phone i don't wanna change it for other yet.