Don't want to burst your bubble too much but I ended up reformatting and reinstalling Windows, issue went away.
Then built a new computer with a different CPU, Motherboard, RAM, new SSD (with yet another fresh Windows install on it) only for the issue to return on this completely different system.
I think it's a very weird combination of a number of factors, between Windows, iCUE, GPU drivers.
I've been fighting with it for months on two different computers.