DIRECT ANSWER
Connect only the Xbox controller for the first setup, bind steering and throttles, add a small rudder deadzone if needed, and use the mouse cockpit controls to distinguish an input problem from a power problem.
Baseline profile
Keep essential ship controls separate and test every neutral state.
- Left stick: steering or rudder
- Triggers or stick axis: throttle only after checking neutral
- Buttons: engine and view commands
- Mouse: clickable cockpit fallback
- Add other USB controllers only after this profile works