I have a 2010 328i BMW. It’s been fine with the exception of run flat tires, which we’ve switched out of…my present problem is with the car pulling to the right when braking on very wet roads. This doesn’t happen below about 40 MPH, or on dry surfaces. The shop has checked the brakes twice, and done an alignment. Is something getting wet that shouldn’t, or is there an adjustment that hasn’t been explored?
You may not be able to do anything about it. It may be that one set of brakes, the left side in your case is simply getting wetter than the other set. There are shield under the engine compartment to deflect water away from critical areas like the air intake and the accessory belt(s). the shields may not be symmetrical for design reasons and therefore, nothing you can do about it.
It is also possible that a shield has been damaged from road debris, they could look at that.
Has a BMW-only shop been consulted? BMW’s are know for their excellent brakes. You may just need somebody with more BMW specific experience to take a look at it. It’s probably something simple.