Epson PRO Reference Manual page 47

If you are using a PC, your Windows video driver might not be
compatible with the printer. Use the standard Windows VGA
driver or contact the manufacturer of your video card for an
updated driver. For information on changing the video driver,
see your Windows documentation.
Replace one or both ink cartridges.
Vertical lines do not align .
Calibrate your printer as described in the Setup and Software
Guide.
You see white banding in your printout.
Turn on MicroWeave in the printer driver.
Clean one or both print heads.
The printout contains incorrect or garbled characters.
Make sure EPSON Stylus Pro or Pro XL is selected as the
default Windows printer driver (PC driver) or is the last printer
selected in the Chooser (Macintosh driver).
If you are running Windows, make sure the Print Manager is
turned off in the Control Panel Printers utility; see your
Windows documentation or online help for instructions.
Print jobs may be held in the EPSON Spool Manager
(Windows) or the EPSON Monitor2 utility (Macintosh). Select
any print jobs marked pending, waiting, or held; then select
Delete or Cancel Printing.
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Maintenance and Troubleshooting