It seems like this machine is giving you a lot if issues. Where did you buy it from? Can you go through them rather than HP?
Other things that might be the issue, having no idea what your set up is or what has been done or not done.
When was the last time the print heads were replaced?
Did one of the ink cartridges accidentally get damaged or put into the wrong place?
Have you done a CMYKlclm test print? Do the colors come out fine there?
Have you tried to create you own color profiles for flexi?
Is the encoder strip damaged or dirty?
On the maintenance cartridge, is it purple on there as well?