Annoying rattle like sound in the 50hz Pulley & Screw in the Project Xpression III

My Project xpression iii starts with this annoying rattle like sound after a couple of hours running. I've checked that everything is in place, that the band is not touching anything and that nothing is interfering with the normal spin of the Pulley & screw, im looking for some suggestions to stop the sound without unscrewing the whole area just to see what it is. Anyone who has had this problem?