On the left side of the glass, you will see other but small glass. That are is used to scan docs from Auto doc Feeder. Try to clean that area. It maybe dirty.
When you do a copy from the glass, the lamp will move across the glass, but if you do from the ADF that same lamp go to that small glass area.
Our workcenter 5735 prints a line across the bottom of each page when using the sheet feeder, but not when copying from the glass. Any suggestions on how to get rid of the line?