Urrrgh, sorry your build experience has been terrible

Essentially as you have said, the issue lies with either the CPU, RAM or motherboard.
IMHO the most likely cause is the CPU because:
(1) The ram is rated to run at 6000c36, so unless they chips are binned wrongly this is unlikely to be the issue
(2) You're not going for monster over clocks, and the mobo supports 6000 ram, yes there are sporadic reports of incompatibility, but these are usually the very vocal minority (ie no one will post if the board works fine...if there was a more endemic issue we would, I hope, have heard more about it seeing as the b650m HDV/m.2 was very very popular)
(3) Leaving the CPU as the most obvious culprit as you are indeed asking it to run out-of-spec with an overclock