We recently installed several 269 motors on opposing sides on the drive to our robot.
In autonomous we could not set them to a “neutral” position in which there was no bias signal. This was observed when all power was removed (a zero motor setting) and the robot allowed to “roll” to a stop. It did not roll straight, it swerved to one side. This was because, even though a zero setting was sent, the motors had a bias signal in one direction. You could feel this simply by trying to turn either wheel attached directly to a motor.
Since the motors were on opposite sides, the bias caused one side to resist going backwards and the other motor encouraged it to go backwards, hence a torque on the robot.
Since this ws entirely in autonomous, not transmitter trim was involved. New motor controllers were used.
Quite frankly it appears like a cheap and nasty motor design. It makes programming in autonomous more of a challenge, but you would expect when a zero siganl is sent there should be no resistance to trurning, except for the mechanical resistance of gears within the motor.
Should this be occuring?