I had to adjust the white screws on the collimator body until the belt stopped slipping. In fact I took one of them out completely leaving just the one to add tension to the body. Other than that,and the velcro added to the motor shaft nothing has been stuck to the collimator body. One other point now that you have removed the cover/door I would be more inclined to block off the gaps that have now been introduced around the lens body so as to stop dust getting to the grating itself. Got the idea from Paul Lukas (second photo down)..