As with all E36's my 316i compact (1995 euro model) has a central locking mechanism on the 3 doors and the fuel lid on the right panel between the front door and rear wheel.
Just lately I discovered that the lock on the fuel lid isn't working.
I removed the interior behind the fuel filler, to find out the the actuator is present, and working. When I reverse the wirering, the pin pops out when I unlock the car. But when I connect it the correct way, it will only retract, not pop out...
After a long afternoon trying to sort this out, I found out that the does pop out, but only when I lock the car with the rearhatch lock. Using one of the doorlocks, the fuel lid remains unlocked...
Is this normal? Or where should I search for any malfunction?

the actuator itself when unplugged and in hand should move in and out smoothly with a little pressure. sometimes you break some teeth in it and it gets sketchy and hangs up on the broken pieces in there.

It sounds more like you have some strange gremlin in your wiring to me .
im not sure if all bmws do the double lock from the key fob i think some older models only double-lock when you use the key on the rear lock like you mentioned.

i would search more on the double-locking and see if there are threads on how to tell if your car does indeed double-lock from the key fob or just the key. hope that helps.