If he's worn the cush drive rubbers enough from the cush moving fore and aft, it will let it move some side to side. Not an even side to side movement, more like it's pivoting on the spacer side to side. I had the happen before with some extremely worn rubber isolators.
Get the new parts and install. I used a light application of dialetic grease on the rubber to help install.
Get the new parts and install. I used a light application of dialetic grease on the rubber to help install.