Stop Motion Knob
 

Suddenly the stop motion knob (the one you loosen to wind bobbins) is loosening while I sew. I can't go more than 10 inches before it loosens and acts like its winding a bobbin. I have tightened it as tight as I can but it won't stop. Its a Janome 1000HD. It doesn't have more than 30 hours of use but it was fine until today. Any ideas?

If it has that few hours on it I'd take it back to the dealer.