2006 Mercedes-benz E-350 automatic door lock problem

My son owns a 2006 Mercedes-benz with an automatic door lock problem on the right front passenger door. All other doors work fine, when the transmission is in drive and you start to move forward all other doors work just fine EXCEPT the right front door. That door will chatter several times and sometimes end up in the locked position and other times in the unlocked position.

I think the problem exist in the solenoid or module which mechanically operates the lock mechanism. Is that part replaceable by itself? What is the part number of the part? I am looking for a diagnosis, suggestions, any and all help that you may give me. Thank you , schaffer81

I believe you are on the right track. The door lock actuator may need to be lubricated or simply replaced.