I can reproduce this problem on my non-Threadripper Ryzen 5 3600 Zen 2 CPU. I don't think it's specific to TR.

With AVX2 enabled, Prime95's torture test is only stable when I use 3 workers or less. With 4 workers one of them will abort due to an error within 20 seconds. The more workers, the sooner a crash; with 5 workers it happens within 10 seconds, and with 6 workers it happens within 2-3 seconds.

If I play with the tests on and off for a while, seemingly increasing the quiescent temperature of the CPU, the whole experience and testing actually becomes a bit more stable. My motherboard uses the B450M chipset.