Computer shuts down during gaming

I recently got my hands on a Sapphire RX 6800XT, and added it to my gaming PC. Initially it went pretty smooth. Then, a few days later my computer shuts off while playing Divinity 2. No bluescreen, just off. As if someone pulled the plug. Now, I had a 9 year old 750w PSU, so I figured that the new card was spiking and overloading the PSU, and it was time to upgrade. So I got a seasonic focus PX-850. In the time it took that to arrive, I encountered the problem in Deep Rock Galactic and Assetto Corsa Competizione as well.

Once that was installed it it seemed fine. I bought a VR headset around the same time and went to try it out with ACC. Within 15 minutes the computer shutdown on me again. In the same way it did before. No bluescreen. Nothing in the event viewer. The problem still exists in VR, and out. But only in games, benchmarking software wouldn't do it.

VR seems to cause this problem to surface VERY quickly. Usually within 20 minutes.

A friend of mine that lives just around the corner has a very similar card. Same manufacturer, but it's a 6800, not an XT. I borrowed his card for a week or two, and he used mine. Neither of us had a problem. I did everything I could to coax this problem out, but it was perfect.

I took over my VR and sim racing equipment to his place to test my card in his machine, and it was just fine.

It doesn't seem to be the card because it works in my buddy's machine. It doesn't seem to by my PSU, because his card works fine in my machine. I'm out of ideas for what might be causing this. Nothing quite fits all of these tests. It seems like a power issue, but it's a brand new PSU that has more than enough wattage. Does anyone have any ideas what might be behind this?