Does the top bulb on the left side turn on when the rear fog is enabled or is it on when the lights are on in general?  On some models, the rear fog only lights on one side as per European regulations.  

Let me know if the top left bulb is not related to the rear fog...

Hi!

Just changed the battery and alternator on a 2012 Mini Countryman S. Noticed the right side's topmost bulb was blown. Bought a new bulb and changed it but still not lighting. Took out a working bulb from a position below and used that, but still would not light.
Took out working tail light assembly from left side and swapped with right side. Still the topmost bulb on right side will not light. (Left side good). Swapped it back and still right side topmost bulb not working.
Took apart tail light connector and measured voltages on the pins. Pins 4 and 6 show 2.9Volts on bad side. On good side only pin 6 showed a voltage. So something is different between the two connectors.

Any ideas on how to troubleshoot more please?
Appreciate any help!