I have the same problem. I removed the glass so I could see what was happening. The scanner head moves OK but when first turned on drives in fits and starts until it reaches home but it doesn't know it is home so it continues to drive making the clicking sound as the gear driving the toothed belt slips over the belt teeth. If left it will probably will wear off the belt teeth. I don't see a limit switch nor anything that resembles a "I'm home" position sensor. Good opportunity to clean the glass inside but it won't he;p if I can't get the scanner to know where it is. Any offers or suggestions?