You make a valid point SoNIc, but I’m still not convinced by the power supply theory because I was running each Pi with just a dongle in early May and added an LNA to each Pi (and enabled bias-t) in June so the power requirements have been much higher since than they were when it happened.
The other thing is, my router and switches didn’t seem to be affected because according to the logs provided to me by the monitoring service I used at the time, availability of my web and email servers never changed.
Perhaps it was just a very strange coincidence that they were running perfectly before I put on the updated jsons and have been running perfectly ever since I put back the original ones.
Something else maybe an o/s update?
I will probably never know, unless it happens again…