doors,Front Passenger Lock sometimes does not lock with a remote control or by locking button located on either doors.

Greetings: When locking the car using either with the remote or with the lock button located on either doors, the front passenger door sometimes won't lock. All other three (3) doors lock every time. Is solenoid part of internal door lock? So if I purchase the door lock to replace the faulty one would fix this issue? Thanks

My car has 140000 miles.
My car has an automatic transmission.