Had an issue with a customer mowers a few years back, may of been the same model. In his cause his wife was mowing, and heard a pop, and then the deck wouldn't engage. After close examination, found that the frame around the engine mount has stress relieved, and the front of the engine drops about the thickness of a washer. Because of how far the deck drive pulley is located from the engine, it moved the deck drive pulley on the engine back about 3/4 inch. After shimming the front of the engine with a washer, has been working fine since.