The Quickie Q500 M is a complex power wheelchair where joystick drift can come from the joystick module itself, calibration/software settings, or wiring/controller issues. Because mobility reliability is critical, repairs should focus on restoring predictable control: verify joystick calibration, inspect connectors, and test the controller input signal before replacing major parts.
If the chair is under a few years old and the motors and batteries are otherwise healthy, replacing the joystick or control module can be a strong repair decision, even if parts are costly. Replacement becomes more appropriate when multiple systems are failing (electronics plus batteries plus seating actuators), or when you're experiencing recurring control faults that compromise safe indoor maneuvering.
Also factor in clinical needs: if seating support requirements have changed, replacing the chair can deliver improved positioning and comfort that repairs won't address. When comparing costs, include labor and programming time, since chair electronics often require dealer setup.