ON 12/20/2017, ENGINE FAILED @ 18050 MILES AND CAUSED INSTANTANEOUS LOSS OF POWER IN TRAFFIC. ENGINE FAILED DIRECTLY OFF LAKESHORE DRIVE IN CHICAGO, WHICH HAS NO SHOULDER. A STRONG SMELL OF BURNING PLASTIC AND RUBBER WAS EMANATING FROM THE ENGINE COMPARTMENT AFTER THE BREAKDOWN. VEHICLE WAS TOWED INTO DEALERSHIP AND REPAIR TOOK 40 DAYS, AS ENGINEERS IN GERMANY HAD TO BE CONSULTED ON THE PROPER REPAIR METHOD. SERVICE ADVISOR INFORMED ME HE WAS "SURPRISED THEY DIDN'T PUT A NEW ENGINE INTO THE VEHICLE". UPON THE VEHICLES RETURN TO US, ON THREE SEPARATE OCCASIONS THE VEHICLE REVS DROPPED SUDDENLY AND WE EXPERIENCE A SEVERE DROP IN ENGINE POWER FOR 2-3 SECONDS, ONCE WHILE TURNING AND TRAFFIC WAS HEADING TOWARDS OUR CAR. VEHICLE WAS RETURNED TO DEALER FOR FURTHER REPAIR BUT NO ISSUES WERE FOUND AND WE WERE ASKED TO TRY TO GET VIDEO RECORDINGS OF THE ISSUE. TO DATE THE VEHICLE HAS BEEN OUT OF SERVICE FOR 45 DAYS, AND THE ISSUE ALMOST RESULTED IN CAUSING AN ACCIDENT.