Rear door doesn't always unlock

[DallasDave X5M]

I didn't see any related posts, so I thought I would create one. About 40% of the time, the rear passenger side door will not unlock properly. It doesn't seem to matter if you unlock the doors via the remote, opening the driver's door when the car is locked, or using the unlock button on either front door.

Yesterday I stopped for fuel. During the fueling process, I attempted to open the rear passenger side door. It wouldn't open. I opened the front passenger side door normally. I closed the front door and used the key-fob to lock/unlock all doors. Again, all the doors would open except the offending one. I then opened the front passenger door again and this time pressed the unlock button located on the inside panel. Same result. By now the fuel tank was full, so I finished paying, etc.

I tried one more time. I locked all doors, then opened the front passenger door by grabbing the handle. This time, the rear door unlocked too.

Is this just a simple lock actuator replacement, or something else?