iMac 27 2014 problem

[TheSufle]

tell me what the problem is, from time to time, green bars appear during boot, and after that the computer continues to work stably without failures

All this appeared when electricity was lost during operation.

 

[robbieduncan]

I’d say the GPU is damaged/dying

 

[TheSufle]

the fact is that this is only during boot,after loading it works without failures