Seems to me there are two challenges here:
1st. Understanding what has caused this....and
2nd. Fixing the wrong-way switch itself.
The earlier contributors are clearly the ones you need for "1st."
I'm more the "do the 2nd" type. I suggest making a new in/out cover for the switch with a labelmaker, and putting the "in" end on the one that causes the air to come in, and etc., etc. with the other. Now you don't need to bother with the 1st!
Hope to meet you somewhere down the road.