Microwave turntable rotates when door is opened

About a week ago when I heated my lunch (Hormel: roasted beef, mashed potatoes and gravy) in a GE microwave oven, the lunch exploded as the holes I poked on the top film are too small. I stopped the microwave by opening the door, cleaned the mess with a rag. Now the turnable rotates when the door is opened. I have unplugged it and reseted the clock but the problem is not solved. Other than the rotation, the microwave functions normally. What causes this? Can this be fixed? If yes, how?