White dust and focus, now that's a hypothesis.So, three for three..
The last one I think lived a hot life. There was a lot of white dust inside and parts of the black plastic PCB covers were starting to crumble. I blew out the white dust and then felt oddly energetic and focused.
Anyways, after the PSU replacement it booted right-up. Seems to have come from the same place. Config had lots of VLANs. This one started at 2000 and I stopped around 3500.
Thank you once again fohdeesha for your wealth of knowledge and to everyone else who contributed to this thread!
That might add up to the assumption/hypothesis that maxing out the POE usage will lead to running the PSU near its rated load, thus the resulting heat/insufficient passive cooling might be the cause of early PSU failure? Would be nice if one could cram a 40mm fan in to prevent future failures if running at more then several POE devices. Of course, that sort of kills the part about being solid state/silent. Just something to move air over the PSU with a very low noise rating would be a good idea. But to find something that will run at ~50V? might be tough for a 40mm.