Switch Failure

[RebusCom]

Yesterday I had a production WS-12-250-AC switch spontaneously fail with no warning. It's monitored for unusual log entries, etc. All traffic stopped and the unit was inaccessible. Arriving on site I found all lights on looking pretty much normal but when I cycled power the port lights (all are in use, mostly POE) illuminated on only one port and all others remained dark. For expediency I swapped the switch out with a spare and took the offending one to the bench.

It was still inaccessible when powered up and no port lights other than the Ethernet on the one connected non-POE port. Holding the reset button with the unit powered up did nothing, no lights, but holding the reset button while powering up did seem to clear things up once the reset completed. I applied the backup config successfully and updated firmware from 1.5.5 to 1.5.6 with no issues. GUI indicated voltages are fine.

Not wanting a repeat, is there a more thorough test procedure for memory, etc., that is recommended or suggested? Any ideas as to cause? Not sure I can trust this unit in a production environment anymore.