Ok, so the crashes may not have been so odd – my UPS might be dead 🙁
I (finally) made up a simple APC UPS cable, and built apcupsd for the Qube. Logging looked good, with 60 second health entries in the log file. Pressed the Test button. Server goes off. Oh sh…
Tried the mains switch on the unit and the wall, and noticed that the LED in the power switch only comes on for a few seconds after initial power up. The reset switch on the back looks good, so I guess the battery is done for.
Annoyingly, that last crash has also wiped out my uptime database, so for the record the best time was 50 days. I’ll have to check things out, but it might be that CPC have a UPS on offer for less than a new battery for the current one.