The fix passed the PNW winter with flying colors. The trunk and the battery compartment are now dry like the Atacama desert
Even the SA was not aware where these flaps / rear vents are. He had to talk to his foreman. It seems that there are 2 options to get there: either remove the rear bumper or remove the wheel arch liners. Not sure what they did. I can go and ask if you insist
P/N:
https://www.ecstuning.com/b-genuine-...n/64226909340/
I don't think that it's a design issue. Otherwise there would be thousands of people complaining. It's probably a manufacturing issue and/or the quality of the first rear vent was not closely looked at. My car was produced during March 2009, so the very first batch.
Looking at your pictures, holy cow, you better fix this ASAP at your BMW dealership and ask an indie shop to give a closer look at the underbody rust, maybe apply a coater such as Rust Oleum.
Good luck. Peace.