I'm in the same boat with a t-jet Jumbo2. Nothing but problems since day one. Spent 16 hours today printing shirts and it takes 2-3 underbase coats to get anything white. The techs have been out several times, replaced countless parts and this whole fiasco has been going on since August.
I run a top 2000 website (in the US, 3500 worldwide according to alexa) and we normally sell a thousand tshirts a month. Since switching I've sold none, except what I have left in my overstock from when we were doing screen printing. Considering the investment I've put into this machine in the start up costs, I deeply regret it. I hope tomorrow there is some kind of resolution (just had another tech service call).
Everything I've read says Blazer Express/Pro is the way to go. I wish I hadn't fallen for the "upsell".