Did your test prints simply drop out the nozzles, or did it begin with some deflection and grow into a larger problem?{YES} One thing that came to my mind was the possibility of static being generated as material is unwound and fed into the printer. It would be even more of a possibility if your material is on a polyester liner. Usually, static is brought up as the culprit when no obvious concrete causes are seen, but, static can influence the "flight path" of the ink droplets; even to the extent that they rebound back onto the head's membrane. You can use a static meter to see if there is infact a charge, or just put your hand near the vinyl (top and bottom) as it comes off of the roll. If you find a charge, you can discharge it with tinsel, or a high-dollar deionizing air knife.
Most likely, static is not the culprit,{ I have total climate control, so static is not the problem. Also static will USUALLY cause deflection across all colors. mine is black only} but it would be good to negate that argument before your tech gets the chance to blame the problem on static and leave you hanging.
If the defect is more like a large dot rather than a misty spray, it may be that ink is not getting cleaned off of your print head, and subsequently dripping.{ Not the issue here} That scenario could be caused by a damper that is going bad and not able to regulate the flow correctly, a head cap that is deteriorating or even a bad wiper.{None of these are the culprit. All of them have been changed and are new.}
To check the damper's condition, take the cover off of the carriage and look on the left side of each damper as yo are facing the carriage. The round window should be flat. If it's bulged out, replace the damper.
As for the wiper, if it is at all warped, change it. Make sure that when cleaning the wiper that the back side; under the curved lip is clean as it is the working edge that comes in contact with the head when it wipes off excess ink.
When it comes to the cap head, make sure that there is no plasticized ink around it, and that it's not deformed. It needs a good seal in order to effectively clean the head.{ I keep this machine meticulously clean. My tech cannot believe it is over three years old.}
If all of those are in good order, the next thing to look at would be the pump right below it. Make sure that when the capping station gets filled with wash fluid, it stays there as opposed to quickly draining out. You can also put a volt meter on it to make sure it's getting adequate power.
All of those parts are cheaper than a head unless you have a parts warranty.
Wish I could be of more help, but I am only learning this as I break mine!
Good Luck!
