Hey bunnelaire!
I'm here with some hope (but maybe not the right solution for you). I had the same problem a couple of weeks ago on my new PC. Eventually I solved it by realizing my RAM was not clocked properly. I had overclocked to 3200Mhz, but my settings in the Ryzen DRAM Calculator were a bit off. Namely, i had my RAM set as A0 instead of A2. I suspect this resulted in timings tha twere slightly off for my hardware. If you have done any RAM overclocking or if you have done any CPU undervolting/overvolting or GPU overclocking/overvolting, I would highly recommend you doublecheck that your settings are correct. For me this solved the issue completely. I haven't had any crashes since doing that fix.
Good luck!