Good news, if you don’t feel any resistance at all that means it’s only a software issue!
My guess would be that we made a mistake while configuring your motor. They all have internal motor limits and we must have set them incorrectly.
To set the good limit position you can run the following code.
from reachy import Reachy, parts
reachy = Reachy(
right_arm=parts.RightArm(io='/dev/ttyUSB*', hand='force_gripper'),
)
motor = reachy.right_arm.arm_yaw._motor
motor.rot_position_limit = [-90, 90]
Then, turn the robot off and on again to make sure that your new configuration is taken into consideration.
Let me know if it solves your issue!