Canon IPF8300 drops out red

Hi everybody. I could really use some help on this one. I have a Canon IPF8300. I have replaced the right side print head three times. The right side seems to last about a year and a half or so. The last time it was replaced was 7-15-15. It wouldn't print red. I did a head cleaning A then ran a small sample and it printed the red. I thought great, so I printed a large print and about 3/4 of the way through the red banded and quit. I immediately ran a nozzle pattern test and there was no red at all. I thought since I already did a head cleaning A, I would do a B and then run a nozzle pattern again. This time the red was there but lots of missing lines. Canon is saying it is some kind of carriage vacuum issue and not the head because it happens to often. Does anyone have any thoughts or should I just replace the head again? I have lots of Giclee prints to do and need to get this up and running but can't afford 1500 - 2000 for someone to do it.
Thanks in advance for any help I can get.
David