Review this guide [guide|50496] See if the part of the blade assembly that connects to the base is secured to the blade within the glass vessel. also check to see if the you start the motor the block on the top of the base that grabs the blade assembly is turning. Take a pencil to see if the block is not lose when you start the motor use care as you don’t want the pencil to fly off! Just press it lightly along the wall of the block.