Follow-up on this issue. Turns out that the brake lines had completely corroded on the left side of the vehicle and burst.

Because of the low mileage nature of my X5, the hypothesis is that over the past few winters, the heavily salted slush from Chicago's roads covered the lines underneath and over time corroded the steel lines. The covering over the lines does not allow sufficient drainage, thus water pools easily. One of the first questions I was asked was if the car was ever involved in a flood.

I was curious as to why this was never noticed and the mechanic indicated that the lines are very challenging to get to and thus aren't inspected.

I recently heard from the same shop and they have begun inspecting all X5's that come in for this issue and have definitely found a pattern. It seems to me that BMW has created a serious problem here.