It has not happened since. But i don’t modify programs often.
Timing wise, I was right in the middle of modifying programs on my android phone with the OS app when it happened.
Pure speculation, but perhaps doing the program update coincidentally just as the NTP was syncing is what may have caused it.
What somewhat unexpectedly surprised me is that it only caused the Ethernet to lock up (sprinklers kept going on and off as expected).