Bruno747
Did some searching but didn't find anything after a short bit. Actually search said it found nothing at all with most of the search terms.
 
Anyway. Got my $1881 3090 FTW3 Ultra today. Most things running okay, but fallout 4? Horrendous.
 
I can walk around, but the moment any action or explosions start it crashes to desktop. Not only that, this 3090 actually has a significantly lower frame rate than my 1080TI did in high stress areas. Yes I have mods, but my 1080ti didn't crash a single time over the years. What gives?
 
Is there a fix for this or is it already time to start speaking with EVGA about RMA or returning this card? Kinda furious that an almost $1900 card cant play something from several years ago at the same level a 1080ti can.

Could be driver related.  You will need to try several drivers before blaming eVGA for this.
 
First, try 456.98 Hotfix.  Yes it's an old driver but a lot of people liked this driver.  Most of the complaining came from people with those 4k OLEDs having artifacts due to monitor firmwares and incompatibilities.  There were other complaints but nothing as bad as the current last two game ready drivers released.
 
Use "Display Driver Uninstaller" in windows safe mode before installing 456.98 hotfix.
 
Next, if THAT doesn't resolve the issue, try 456.38 *studio* driver.  NOT the game ready driver.  See if that changes anything or not.   Again use DDU before installing.
(keep in mind that "For Honor" will not work with 456.38 studio but will work with 456.98 hotfix, which is one of the main fixes in that driver compared to whatever the previous game ready driver was).

Good luck and report your results.

I play Fallout 4 VR a lot, game runs great.  I'm running 400% super sampling, nothing ever came even remotely close, not the 1080, 1080 Ti, or 2080 Ti.  I had them all.  I also have the same card as you currently.  You may want to consider flashing the XC3 BIOS, it will improve performance in games for you by increasing your power limit.  Of course you'll have to stick with versions 1.1.1 of Precision X if you do that, and no matter what, don't ever update the firmware if you are running that BIOS if Precision X asks you to.  You should check out the thread about the 500w XOC BIOS if you want to learn about the XC3 BIOS, most of us on there are running it.
Although, I did have to run a lower clock speed to maintain stability in Fallout 4.  I have run into a lot of weird issues with that game over the years.  I don't know if you're over clocking, but I stuck to 2025, where I am stable at 2070 in most other games.  Having a higher power limit will prevent the voltage from bouncing around all over the place, which that itself can cause instability.  If you haven't set your power limit above 100%, max it out, not that I expect it to work unfortunately, if it does, you got super duper lucky.  Or, if you don't want to flash a BIOS, you should try fine tuning the voltage.  If you've never done that before it can be a bit frustrating and very time consuming.  What I have always done is set the maximum voltage (1.1 or 1.093, although tbh I rarely see above 1.081) to whatever your highest stable clock speed is and drop 10 MHz for every voltage point.  If you can't do that, I would just try running a lower clock speed and don't overclock your VRAM until you're certain your core clock is stable.  Start at 1900 MHz and work your way up for GPU core.  You shouldn't have to do anything but set the clock speed and that speed should be fine on stock BIOS, also, crank up your fans to 100% to eliminate thermals as the potential problem, actually, you should start with that, and maintain it until you've figured out the problem.  I would try to keep temps below 70C regardless.

Does underclocking the card to max negative values on the core/mem inside msi afterburner help stop the crashing?

Did you overclock？