I second that with SteveFehr. Measure all individual circuits with a clip on ammeter and work out which one has a high unexplained use on it.
Then trace back which appliance is the culprit.
Also the meter was checked by the POCO ? I have done field meter testing for over 10 years in the POCO and meters rarely fail.
Generally they tend to be slow when bearings wear out.
A lightning strike may damage the brake magnet sometimes but you have guaranteed damage to home appliances as well.
Electronic meters are very accurate but are known to have sometimes unexplainable errors when capacitirs fail on the internal circuitboards.
Even 40 and 50 year old meters are still well within their accuracy class.
Good luck with your findings !
