I have a panasonic convection oven model NN-CD997S My turn table works fine with a light load but when I put in a roast into a roasting dish to cook I find that the turntable jerks in short bursts in left to right and right to left motions. It does not complete a full circle. The motor may be labouring. Do you think replacing the motor would solve this problem.or do yo have a suggestion? After opening the unit and checking I feel everything else looks OK Regards Fernando