Why is my screen flickering like a kaleidoscope?

The screen shortly after logging in flickers, redrawing the graphics incorrectly, almost like a memory issue. The issue occurs on a second monitor also. I considered it could be software, but then experienced the same issue when about to do a time machine restore, by pressing command and R on reboot. Previously the laptop has had the vcore recall, I haven’t checked, but was advised my whole logic board was replaced vs just the rubber square stuck-on the vcore chip to apply pressure and improve contacts. In any case the flickering presented now is different to the issues then.