Make sure the paper feed side plates touch the paper lightly. Shift the lock lever backward.
If you use the ADF, make sure the original guides contact the originals lightly.
If blank or incomplete prints still occur even after you have checked the above, perform the following procedure:
Unlock the lever and pull out the drum unit.
Remove any paper wrapped around the drum.
Remove the master from the drum.
If you cannot remove the master, open the clamp by releasing the lock lever at the back of the drum unit as you pull out the master.
Push the drum unit until it can go no further and locks into place, and then lower the lock lever.
Close the front cover.