I don’t remember what it is but there’s some major flaw with those Mini engines that makes them fail after 50-75k and they need to be rebuilt. My nephew buys them totaled from insurance when this happens, rebuilds the motors and flips them.
the older sc ones are prob more reliable but suck. the 2008ish or whenever they went turbo had under hood temp problems, direct injection hpfp problems, and realllll bad pcv recirc problems. the first two were were resolved for the most part around 2010/2011 with some design changes. the pcv was ****** - it was all handled in the valve cover so you couldnt catch can it and recirc'ed directly through paths in the head into the intake port, with no port injection they had massive build up on the back of the intake valves after like 30k miles.
after i cleaned mine at like 50k i drilled and tapped the ports in the head and put in some setscrew plugs and ran the pcv out of the cover....a little more than the average person was willing to do
the like 2012,13,14 were all pretty well smoothed out, but then model change and they started using the bmw b38/48 engines