I would send it in for sure, something is up, its unfortunate but it sounds like MacDev may have sent you a lemon. It has got to be something faulty with the board or solenoid.
You said you've checked the Orings, re-lubed the reg and drivetrain, installed a fresh battery, and made sure your air supply is good? What else could it be at this point? I hope it has to do with an electronics issue and not a machining quality issue.
Keep us posted on how well MacDev takes care of you.