>I don't know how to interpret your l=
ast comment 

Yeah, I was a bit unclear. I was just indicating that while I can workaround
the issue, it can still be triggered on my system as well. E.g. if I switch=
 to
75hz, it will be stuck at 850mhz (even after switching back), so it's possi=
ble
that the issue can be triggered through different ways (but the underlying
issue may be the same).=20

Anyway, I suspect that this bug, the one related to sensor readings (includ=
ing
the 75hz issue), are all related. It's most likely a video bios/firmware is=
sue
as it affects Windows as well, and some have even triggered the bug in BIOS
settings, with monitors that use 75hz.

One thing you could try is booting with a window manager/DE that doesn't use
any sort of hardware acceleration. That's the main difference I can figure
between my system, and yours (besides the fact I use x370 instead of x570).=
 I
would also try a lower resolution just to test, as that's a pretty non-stan=
dard
res, and might be another way of triggering this bug.