Quick and dirty way to try out if it is indeed thermal throttling: Leave the side panel open, see if it still happens. As for the 180W thing, most (if not all) Vega cards have different profiles that limit power use to 150 / 180 / 210 / whatever, should be accessible through the AMD Wattman software, have a read through here: https://www.amd.com/en/support/kb/faq/dh-020 Note that some 3rd party software that can influence how the GPU behaves (MSI Afterburner and such) can cause conflicts with Wattman.
That's far under the safe operating temperature for modern VRMs (which will operate comfortable north of 100°C). GPU-Z reports PerfCap Reason (what's causing a card to throttle, which could be thermal, power, voltage, etc) for Nvidia GPUs, not sure if AMD drivers also expose that though. The 180W limit would match operating in BIOS 2 Gaming Power Save mode. IIRC these are set via DIP switches on the back of the card under the power connector, so could have been inadvertently bumped. However, the card blanking out is definitely not intended behaviour for any sort of throttling. That could be a driver crash, or it could be a hardware fault (usually memory).
I know it's a noob thing, but my far more experienced PC chum managed to nearly break his 2080ti by using one power lead from the PSU with 2 ends plugged into the card. When he used two GPU power leads from the PSU, his issue went away. I would expect this is not the actual problem, but sometimes the simple solution is the best one?
My devil 64 can't even run stock tbh. You desperately need to under volt it, but I was crap at it it seems lol. I just enable Radeon chill, which did work well and stopped it crashing.
