I presume the cards are identical, same mem etc.
A history of the problem always helps. When and how did the problem start?
It's interesting that only one card has a problem.
The first thing to do is identify any differences in configuration, ie FW,
monitor attached.
If so move the monitor to the other card and see if the problem moves with it.
You could try different algos or miner SW to see if you can reproduce it
with different variables.
You could also try swapping slots to see if the problem follows the card or stays with
the slot.
Swap anything else you can think of that's in the path, risers, power cables.
The symptoms seem like a mem leak but that should affect both cards. If testing doesn't
give any clues I would suspect a HW issue with that card.
They are both new, recently installed and I don’t have any monitors connected to the card, using internal graphics for the monitor. They have same specs and I already tried different slots, power cables etc. I tried the fans right on it which improved temps but still same issue. And it goes back to full hash rate after I restart pc. But simply restarting the miner doesn’t work, the entire system has to be restarted.