Another thing just thought of too if you want to check for a damaged GPU.
Carefully support the card and gently wiggle the heat sink. If still nothing loosen the heat sink and try again. Don’t have any 3D aps running if you do this though and temps should be OK for the short amount of time this should take. If the GPU is damaged this may cause the problem patches to move or go away. Just be aware of two things that could happen..
1. If the GPU is damaged this may make the problem worse.
2. When it’s loose and you’re not careful when wiggling, the heat sink
could touch something and short out the card.
Just a thought hope this all helps and good luck. On the bright side though you have a valid reason to get a better card now
.