The place to begin is to print out and then assess the Nozzle Test Print. On the Falcon Outdoor, this is done by pressing two keys on the keypad at the same time (can't recall which ones, as it's been a year or so since I've been hands-on on that machine).
Look in your user manual or on-line at Mutoh's web site for specifics on this. I would guess that you will be experiencing nozzle problems in one or more colors, perhaps magenta, based on the problem descripton.
If you are seeing nozzle drop-outs, you have a host of things to try:
1) Run cleanings from the Control Panel.
2) Put Isporopyl Alcohol (IPA) into the capping stations on the printer, and then run more cleanings.
3) If it's been more than 6 months, replace the cap tops (2) on the machine.
Hope this helps
Bob