Welcome to the board.
The door locks vary and supposedly there are four different variants.
How do I know? I have the same problem.
I bought an actuator off of eBay from a 2000 coupe. After stripping the door down, I found the actuator was different. My lock had a catching mechanism and the replacement had none what so ever.
Long story short, go to breakers yard and make sure they supply you with the correct part or go to BMW direct. The new lock costs more, but guarantees fitment and working order.
There are good door lock actuator DIYs on the forum. Research is a must.
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More to follow...
WRITTEN OFF BY SOME PUNK BYATCH!
Reppin the U.K