Your new stick is a twist rudder stick and by default the the yaw axis will be mapped to that.
If you unmap the twist axis and set it to none, you can then map the rudder to key presses. However I'm not sure why you'd want to remove the twist rudder but that's what you have to do.
Same thing as differential brakes,if you map them to rudder pedals you cant use space bar to stop.
hope that helps your problem.
