Hello Rafael!
As Drew has suggested, it could be that the current set on the stepper drier is not enough. Have you tried to adjust it?
Could you share the model of the stepper and the driver you are using?
Also, it could be that the torque needed to rotate that articulation is greater than the torque provided by the stepper. Does the articulation 1 moves easily without too much friction?
Best regards,
Angel LM