You have a sanding application and you are worried about vibrations that the sander produces when mounted in the robot arm.
No issues related to the vibration of the sanding kit were ever reported to us yet, but we already had this question a few times before.
UR has verified the compatibility of the sander for use in sanding or grinding applications for continual grinding and sanding under proper programming and robot operation. As in any application, a proper risk assessment is needed to verify system operation and limit hazards. The entity integrating the robot is responsible for due diligence on the robot system and all subcomponents that may fall under that umbrella.
When used within specs, there is no reason to expect premature failure of robot joints.