>>17255695I would say it is still your PSU, seeing as you have to fiddle with it to make it work, it's possible that your video card has already been damaged.
Even though it's 850W, if it's faulty/damaged it will not perform as it should, therefore, order yourself a new one (if you don't have a spare) and try that out. Also, find a friend/family member who'd be willing to let you try your video card in their computer.
If you still have issues with the video card, then both your PSU and GPU need replacing. PSU needs replacing anyway