The recal is a bit flakey, I have the same problem; but on the driver's side.
Like you, I'll have to fix it soon.
Your problem is probably the passenger temp actuator.
I expect your HVAC is like mine; if so, there are two temp actuators on the bottom of the unit.
You need to remove the trim panel below the glove box.
You should be able to see the two actuators, the one near the centre of the dash is driver, the one under the glove box is passenger.
There are some YouTubes on changing them.
Even some on repairing them.
After you remove the actuator (3 screws, I think you need a 4mm socket) try turning the temp door shaft by hand
If it turns easy, the actuator is bad
If it's hard to turn, the door is jammed.
If jammed, try removing the blower fan so you can get your hand in there to clear the obstruction.