Brakes failed, car rolled back dangerously

[byaru1]

So, the brakes failed on me and car rolled back, pressing brake pedal all the way did not help. I bumped into 2 other cars behind which stopped the x5.

The brake pedal would intermittently soften over a few months back, but I had ignored it. The failure was like instant.

What could cause this? My techie says it's the brake master cylinder, but he seems to be using elimination method. He will probably say it's the booster thereafter.

Anyone experienced this?

2007 E70 3.0si

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