Keep in mind, when it loses power the time will stop advancing until power is returned. If it is off for a couple hours it is possible the power loss ride through will maintain the prior time setting until power is restored. At some point, though, the ride through will run out of backup power and the time setting will reset to default (only SETUP or Advanced menu option that resets to default on extended power loss is the time/day setting).
Are you sure it the Coal-trol/stove isn't losing power? Is the fire going out when the time loss occurs?