I had this happen one time on my e28 and burned up my clutch getting home. The problem there was self-inflicted bc I had just replaced my brake booster and had adjusted the rod incorrectly. In your case, I'm not sure if the rod could have slipped and 'foot off the brake' actually means '10% of braking permanently applied'.

when 10% is applied (my rod adjuster thing was only off by a hair) and the brakes are cool, everything was fine. but 1000 feet down the road, the brakes got hot and expanded, then the effective braking was much greater. That's my THEORY anyway. That was right after I learned to work on my own car though and I didn't know what the hell i was doing.

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2005 X5 3.0i - 71k mi (9.2018) -> 81k (9.19) -> 100k 9.21 -> 123k (8.25)
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SOLD : ( 2003 X5 3.0 - 177k mi (9.2018) -> 186k (9.19) -> 205k (9.21)
SOLD : ( 1997 328is Coupe - Hellrot Red
SOLD : ( 1988 528e w/ Bullseye s256 / MS2 Extra / GC Coilovers / Yukon Coils ~ 300+ HP