[Jeron]

I've heard BMW's can be finnicky about bulbs. I normally don't go in fo this kind of bunk. But buying a bulb from the dealer or swapping with the other signal to see if the problem follows the bulb would help eliminate the bulb as a culprit.

I would recheck the socket. Specifically look to see if there is any corrosion on the contacts to the bulb and the contacts at the harness. Lightly sand any corrosion off of the bulb contacts in the socket.

Also, make sure you are replacing the correct light. It could be the side marker. Visually verify which bulb is out instead of relying on the dash warning.