Do you mean that the LEDs blink alternating Red when your robot is Disabled?
That indicates that the SPX is not receiving a PWM signal (which is normal when the robot is disabled).
This is more likely an indicator of the real issue you’re having.
If the LEDs are green, that means the motor controller is attempting to drive full output.
As a test, disconnect your motor and use a multimeter to measure the voltage of the output.
If you see a value close to 12V, then there is likely a connector issue with your motor. If you see a value close to 0V, there is likely a connector issue on the motor output wires.
What color are the LEDs when the motor is not moving as expected? If the LEDs are solid orange then it’s a programming issue, if the LEDs are blinking/solid green/red, then it’s likely related to the connector/wiring issue I mentioned above.