A/C issue/question - 2006 X5

[jbmwx5]

AC system issue - looking for advice/feedback (I tried looking in other threads and didn't see this scenario described)

Outside temp is irrlevant - happens at 80, 90, 100 and inbetween.
Inisde setting seems to be irrlevant - I've tried at Max AC (60), and various temps from there up to 80+
Inside control knob (the one that goes from three blue dots to 3 red dots) - does seem to have an impact. However, I'm not able to roll it to 3 blue dots - but rolling it opposite does warm the air noticably.

Issue - no cold air at all coming from right side (center or window) or rear vents
Left side puts out cold air consistently and constantly - it seems to be at the proper temp.

Air coming from right vents is room temp (or warmer depending on knob and temp setting - so heat seems to work still).

I would have suspected coolant but I am getting cold air from left side and its very cold (temp solution I manually closed off the right vents.

Could this be a thermostat issue on the dual zone a/c unit?

I've turned on off the AC with the car off and then started it.
I've turned on the AC with the car running at low speed and at highway speed, on short drives and after several hours of driving - same in all cases.

Ideas? Suggestions?
any additional information needed?

Thank you!