Craftsmen model 917.272761 deck belts tearing up?

My mower deck belts are tearing up. I put a new belt on the mower and it lasted 2 minutes before smoking and shredding. I replaced both mandrels and idler pulleys as well as another belt and new blades. It started to do the same thing immediately. It appears the belt is jumping around. I checked the engagement spring and seems tight. The idler shaft does have a little play in it. Help please.