If you've got a loose connection on 1/2 of the 240V supply, the charger may start/drop to 120V. That would drop the charging level to the car. Resetting the car may have "rebooted" the whole charging sequence that just happened to have a full 240V supply at the time returning it to the full amount allowed.
Definitely check the connections in the socket and at the breaker box (just to be extra safe). A loose connection is a bad thing to have and can lead to a very hot connection. That situation can lead to a fire. I have a relative who had that happen in a house (causing a fire) and nearly happen in a second house (I detest using "push-in" connections on outlets and switches). I had it happen on a headlight switch in a vehicle but fortunately it only got to the smoking stage before it melted enough plastic to insulate the connection, stop the current flow and the heating.
