Chastity

Got a used 2010 C300 in November. Only issue, is maybe once a week I have trouble with the remote locking the front driver's side door, so I resort to using the key to manually lock it. Problem seems to go away soon within the trip or overnight. Happens maybe once a week. It's inconsistent enough, that I won't leave my car without visually seeing the driver side pin going down.

When I open or close the door, I can hear something knocking around in there so something may have come loose?