How to fix faulty airflow button

Do the symptoms change if you turn the steering wheel? I would try testing it by rotating the steering wheel in 30º intervals and see if it works correctly in certain positions. Test it from full lock left to full lock right, preferably with the front wheels lifted off the ground so the steering gear is not being stressed. If you find that it works correctly in certain positions, it is likely the clock-spring cable has a break in the in one (or more) of the tracks of the ribbon cable.

 

I don't have the wiring diagram in front of me, but often the setup is several buttons sharing one signal circuit by grounding it through different resistances, so a change in the resistance of the circuit (maybe a partial break in the spiral cable, or a deteriorating connection somewhere) would make one button read as a different one.

It might be enlightening to look in the diagram, specifically what it shows for that button and for the other button it's being read as.