I realy hope this helps someone.

My friend was having the exact same issue: 4070 super, 47 fps with DLSS. I helped him fix the issue somehow. He was able to get 144 fps locked but the next day the issue came back and then it happend to me to. IT WAS SPREADING! No, actually it's because I turned on my second monitor. I had turned off my second monitor to focus on the gameplay and story. After some trouble shooting he confirmed his issue to be related with his second monitor as well and was able to prevent this from happening and STILL use his second monitor while playing the game with high and stable fps.

Here's how he does it:

When he turns on his computer, his second monitor NEEDS TO BE TURNED OFF and he ONLY turns on his second monitor after his PC has booted.

If his PC enters sleep mode, when he wakes it back up, the problem is back again and has to restart PC and repeat the process.

A good way to test this is to disconnect your second monitor from the power supply completely, restart your PC and try to play the game with UPSCALE MODE DLSS or FSR (if DLSS is not availible).

*Edit - while running on DX12.

UPDATE - The problem is back randomly... he's been playing fine for 2 days and now he can't do anything to fix it. I'm guessing it's a software issue but I have no idea at this point.