I rebound my helicopter keys such that WASD stayed the same, throttle up and down stayed the same with the addition of using HOME and END, and DELETE and PAGE DOWN became additional rudder controls.

After doing a back flip and flying upside down in the helicopter for some distance and orientating myself the correct way again, I tried to land on the helicopter showcase to re-arm. I could not use any key to decrease throttle, increase worked fine. I could not use my secondary bind for right rudder, original keys worked fine.

I reloaded the save and everything was as it should be. I have not been able to re-produce the issue however I believe it's worth mentioning.