The brief
The 325i's driver couldn't unlock the rear passenger door, it was stuck shut, and the window on that door had been moving slowly and jerkily before it gave up too. He brought it in. A door you can't open and a window that won't move are both the kind of thing that only gets worse, and a stuck door is awkward at best, a problem in an emergency at worst. That door has two things going on: the lock actuator, the motorised latch that does the locking, unlocking and catching, and the window regulator, the mechanism that carries the glass up and down. Both wear, the lock's motor and gears strip so it stops responding, and the regulator's cables fray and plastic guides crack so the glass loses support. On this door both had reached that point, so both needed replacing.
The diagnosis
The door card came off and it told the story: the lock actuator's motor and latch worn, not driving cleanly, which is why the door wouldn't unlock, and the window regulator with a frayed cable and cracked guides, which is the jerky window. The wiring and switches checked out, it was the lock unit and the regulator themselves. That's a lock actuator and window regulator replacement, complete assemblies rather than repairs, coded and aligned afterwards.
The work
The door card was removed, the failed lock actuator and window regulator taken out, and a new genuine BMW-spec lock assembly and a new regulator fitted, the window motor transferred, the glass clamped into the new carrier and aligned so it runs square. The lock was registered as needed so the central locking recognised it, the window cycled to set its stops, and the door card refitted. A check confirmed the rear door locking and unlocking reliably from the remote and the switch, latching first time, and the window running smooth and quiet through its full travel.
The outcome
A rear door that locks, unlocks and opens every time, latches first time, and a window that runs smoothly and quietly. The 325i went home with the door sorted. A failed lock and regulator only get worse until the door is stuck for good and the window's down in the door, so changing both assemblies put it right before it became a being-locked-out problem.