They don't "actually" make their own PSU's. Different OEM's make them. Though I get it, I'll never purchase anything "Thermaltake" again because of a certain stigma they have.
Don't be scared. I've been running my 4090FE since lauch and I have zero sag and the thing is solid as hell. It's built better than almost all other 4090 offerings.
Prior to a reflow, try pressing the card down by the corner while the system is on. Not super hard, of couse, but enough to see some flex. It could reconnect a broken solder joint. If the fans kick on you know that's what it is. Long shot, but worth a shot. If you don't want to dig too deep and...
You could try installing MSI Afterburner and setting a fan percentage just to see if they turn on. Just set it to some percentage and see if anything happens. If nothing, double check that a wire didn't get pinched or something.
This is a fantastic keyboard. I have one full length and 2 TKL and it's a joy to use. One of the TKL's I use with a Corsair lap pad for my HTPC. It fits snug but works great!
Thats how Xbox Game Pass made me feel. When I first got it I was like I've spent over $400 on games that are offered. It wasn't worth it for me then but is now.