But it doesn’t make sense. It works perfectly fine when I run Time Spy or other GPU stress tests?
Yeah, it sucks I know. I had to replace my own PSU for a 3080ti. (As well as a couple customers now). The 3xxx is very "spikey" with their power. Unless you're on a scope you can't get a very clear picture of it.
Take a look at the PSU list here and pick one you like, you'll be good to go: