If it is one of the Export/PT Too family: the belt could come off if the plate is too high from the plinth, or in other words it is not positioned right in the acrylic plate.
Check the clearance between the plate and the plinth that's should be in the range of 5-6 mm.
Good luck
Check the clearance between the plate and the plinth that's should be in the range of 5-6 mm.
Good luck