ESPHome node suddenly went haywire

Last night after weeks, months of pain free operation by ESPHome node suddenly started rebooting constantly every minute or so. I could see from the MQTT debug topic that the uptime monitor was resetting. Any ideas what could cause this?!
It’s connected via PoE and whilst it’s true I don’t know if other devices strung off that switch were experiencing power or connectivity problems I have no reason to believe they were. The overall internet connection was fine and I could communicate with Home Assistant just fine.
The logs of the MQTT broker just show the ESPHome itself reporting a timeout and then reconnecting again and again.
I restarted HA and the problem went away.