hello, i had a similar problem with my bm, i was losing power on corners and my traction light was flashing as if wheels were spinning, even at very low speeds. i did a bit of digging and turns out it was the ABS ring on the rear driveshafts. i took the rear sensors out witha 7mm allen key i think? maybe 6, anyway this gives you access to see the ring down the sensor hole and allow you to clean and inspect it. after cleaning the ring and sensor the problem cleared up for about 4 months but returned. i ended up changing one of the abs sensors and has been running fine since!