2002 coachmen 370ds slide problem

I just recently purchased a 2002 coachmen 370 ds. The first trip out the living room slide would not come out. we could hear the motor but no movement. We used it manually with cranking handle. When I got home I removed the motor to find 2 of the 3 motor mounts snapped off. I can get a new motor but my concern is the wrong bolts where used to mount it which caused the damage. I think it came loose on the two bolts and the motor torque twisted the mounts off. They are slotted bolts that use a flat headed screw driver. This does not seem right and seems that you would not get it tight enough. The motor was replaced at the dealership by previous owner only one year ago but they are not helpful when I called them. Any help is much appreciated.