The output of motion stick has a sudden, instant jump in output at the point of controller being turned around 90 degrees (to either side). The amplitude of the jump depends on the controller position around the "jump point", specifically the more the controller deviates from being perfectly vertical with zero yaw tilt, the more of a jump occurs. If you turn the controller perfectly vertically without tilting it on yaw - it won't jump, and if you turn the controller with slight tilt as you would naturally - the jump might vary from being slightly inconvenient to really intrusive.
To clarify, this issue is also not present with setting MOTION_STICK_MODE to either of LEFT_STICK or RIGHT_STICK, but present when setting it for steering, for example with LEFT_STEER_X
The output of motion stick has a sudden, instant jump in output at the point of controller being turned around 90 degrees (to either side). The amplitude of the jump depends on the controller position around the "jump point", specifically the more the controller deviates from being perfectly vertical with zero yaw tilt, the more of a jump occurs. If you turn the controller perfectly vertically without tilting it on yaw - it won't jump, and if you turn the controller with slight tilt as you would naturally - the jump might vary from being slightly inconvenient to really intrusive.