It has been so long since I used HKN, but something along the lines of a toggle to turn on/off the movement key's?
Because pressing space bar [if I broadcast it to all clients] will break follow while flying, as well as while I am in the water, attempting to jump will also break follow.
Typically flying for me [w/isBoxer] is just a follow train, my space bar only affects the Window/slot I am currently driving from.