There's a factory defect on likely every e53 made where one or both of the year brake pipes below the footwell of the left front seat is bent too much and broke the paint shop it will eventually fail. Badly. If that aligns with where you saw drops that's where to start.

Great you got EWS sync'd!

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)