I would start by bleeding all four corners like suggested and go from there, I would also check and make sure you do not have a caliper/wheel cylinder leaking. Also check the vac line that runs from the intake to the booster for holes or leaks.
Dad owns an X5 and a 650i. The 650 is a total pile of garbage and the X5 was a lemon law but back from California that has had the dash peel up and a rear hatch striker just fall off.
Not as solid as one would think.
Then if you OK with no one from CR showing up, why do you bother logging in here to peddle you little meet out in BFE.
:dumb:I left you no rep, you would know because I leave my name at the end.