From time to time, I would see the following slightly poetic statement on my console.
Uhhuh. NMI received for unknown reason 31 on CPU 3.
Do you have a strange power saving mode enabled?
Dazed and confused, but trying to continue
The first Internet search brought me sadness and dismay - my hardware was failing. It took going a bit deeper to find that AMD servers have that issue quite often even in the absence of real hardware failure.
Solution? Disable darn C-States. It's a server after all.
PS: And no, even if you want to keep C-States, reason 31
is nothing to worry about - it's been happening on my system for 2 years before this and I had no issues with it. It's just annoyance and nothing more.