Our Ridgid Sump Pump- (basement ground water only) seems to be airlocking and becomes very overheated. It is a full submersible and is nearly new. In 30 years of sump pump usage this is the first time we have had a pump that air locks - but we don't know until the warning alarm goes off because the water has risen above the crock top and is on the basement floor. Is the pump defective? We just unplug and re-plug it in to break the air lock and it starts pumping.