The Keybinding screen apply button does not work. Further, it clears the controls that were changed and persists this so they are no longer accessible in game, unplayable.
I did this:
Fire mode, X -> Z
Jump, Space -> X
Freelook modifier, Left Alt -> Space
The error occurs upon clicking Apply. The changed fields are cleared on-screen.
Workaround: Delete local files using Steam -> Verify game files interface