QMS Magicolor WX User Manual page 193

c If you still see vertical streaks, remove the OPC belt from the
printer again, set it on the handle end, and use a soft brush
(for example, the type of brush you would use to clean a
camera lens) to gently clean only the part of the blade that
corresponds to the streaked area on printouts.
Reinstall the OPC and print a page to see if this solved the
streaking problem.
d If you still see vertical streaks, install a new OPC belt
cartridge.