my Larkbox works for 2-5 minutes and then freezes with ripples on the screen, I think this is an overheating of the video card. can it still be revived? how can cooling be improved, what thickness of thermal rubber or copper plate is needed? My version with CPU j4115. The monitor is fully working, the other computer works without problems.
Roll back to the original display driver in Device Manager.
How does it look in the BIOS - the same or without any problem? Also, try another OS, like a live Linux and see if the problem persist(hardware fault), or if its ok, its software (meaning Windows displays driver issue).