On my 99 ML320 , a few times now when I use the remote to lock the doors, the passenger door lock clicks up and down, trying to lock, but will sometimes stay up. I unlock all the doors, try again, and maybe it will lock. Lately it has been ok, until again today, the wife tried a couple times, and ended up setting the alarm off (at least that works fine,and was her mistake). Once home, I pulled the small rubber plug on the door, above the lock mechanism, sprayed a little contact cleaner towards the moving assembly inside, and "Presto!!" it works fine again.
Is this common, and is it just a lack of cleaning or lubrication needed? Anyone else deal with this situation?