It is the PTO belt. Belt and spring come off right after I select the deck level (usually on 1, but today i tried it from 4 graduating down to 1 on very little grass height) and as soon as I pull out the pto button. Well today it came off AGAIN...just had it put on again last nite. We checked for debris before putting the NEW belt (2 hours on it) on so there was no debris in pulleys or belt etc. Guy putting it on for me has a lawn care business and knows what he is doing. This thing is driving me crazy.Shouldn't matter where it was bought the company should make good on it. So it is going into a shop next week. I think it is a design flaw or else something is missing that holds the belt on. Maybe it needs a new spring. But the spring doesn't appear to be a problem.