So I took the front panel off, and removed the little circlip so I could remove the rod and slider.
The slider has a pin that sits in a fork to control the air, and after putting it back on the fork, and putting the rod/circlip back in, it slides back and forth properly.
Then when I reassembled it and screwed it back on to the car, pushing it all the way to the right for the windscreen, it disconnects again.
Not sure what the issue is, but it's easy enough to just leave it assembled use a flat head to hold the fork in the windshield position, and pull the slider back on top of it.