BMW Repair: door lock and window problem, passenger seat, guaranty

Question
Hello Tino
I have a 1991 525i european. I was trying to lock the car using the key but for no reason only the driver door was locked while the passengers doors were still unlocked. I tried to open the driver door with the key but it didn't open. I got into the car from a passenger door and turned on the car without any problem. Yet, the cental locking was still not working and the electrical windows were not working neither although the battery was ok. After around 30 min the central locking and the windows worked again suddenly.
Where do you think the problem is and what should I do to fix it?
Thanks
Roland

Answer
Hi Roland!
After the 30 mins. and central locking and windows  worked again, did you use the key to lock/unlock the driver's door?
If it worked, and by the fact that even the windows got inoperative along with central locking, it seems that you have a general module (basic module) going bad.
It is easy to replace this(it is usually beneath the rear passenger seat--left side), but it still needs coding for which you would need dealer equipment. If you can find a used but working one (get a return guaranty from the used parts seller), then you may not need coding.
But what bothers me is your comment that after things went haywire, you could not open the driver's door mechanically with the key. For even if the central locking does not get activated by the key(thru the driver's door actuator cables)
at least it should open the driver's door.
I hope this helps.
Tino