Hi,

Not sure what pulley it comes off first. We assume it is the engine pulley.
No difference with the deck raised or lowered.
Yes it does fall off when the engine is running above idle.
We wondered if the belt may be a bit loose but it doesn't look as though it is. Whether or not getting a new belt may fix the problem?
Does anyone have a diagram to make sure we have the belt running the right way through the pulleys? We can only find diagrams for the engine belts not the cutting deck belts. Just want to make sure that's all.