Iridesse color consistency issues...

We've had 2 Iridesse units for about 15 months now and have had ongoing color consistency issues. Main problem is that we print a large number of business cards with a solid PMS549 backer for a customer. Color shifts within a run, from run to run and from day to day. Same file, same stock, same profile, etc. Xerox has sent in specialists, escalated multiple times to Level 3 engineering, and sent in countless techs to assess the problem. They have suggested: we're not using Xerox paper, to humidity/environment, to lack of operator training (especially insulting), and everything else they could think to blame it on, even saying that PMS549 was a "special color". Our Xerox technical guy swears it's a Fiery problem, but Xerox refuses to try another Fiery, stating cost concerns. We've even tried printing different color files on consecutive days and it won't hit those colors consistently either. With enough operator intervention, we can get the color to hit, within an acceptable tolerance. I don't think we should be putting in that much work to make the machine print any particular color.
My question: is anyone else out there having ongoing color consistency issues with the Xerox Iridesse?