This is just an FYI.
My friend 2014 E550 with 72k well taken of car and garage had a brake failure the day before he was trading it in.
He said the leak was somewhere in the middle of the car which would suggest the line going to the rear.
No other details but now I am going to check my car out during my oil change and maybe spray the lines down with

 

Either faulty part or rust getting to it. No surprise on the rust part if the car gets driven during winter. Seen it multiple times
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