I'm not sure why the author didn't attempt to dive deeper into the error message he saw. amd_vcn_dec sounds like it's an issue with the GPU's video decoding logic. If there's a timeout when trying to process a decode request, it may be that power management for the GPU is buggy somehow. Given that this is a server build and idle power consumption is likely not a big deal, I'd suggest pinning the GPU power state to see if it resolves the issue (see amdgpu.ppfeaturemask and amdgpu.runpm kernel parameters).
I believe something I call "the window phenomenon" has occurred. Sometimes, life allows you have the time to do these big experiments on your life and then it gets busy again and you can't dive into it with the same capacity, so you have to do what you have to do while surviving what you have at hand.
I have gone through many patches like this, and I believe he had to handle life while is experimental workstation had to limp through.
Then when he had the time, he had just pulled the plug.