Rear drivers' side door window regulator has failed twice leaving window stuck open and inoperable. window was being opened to vent interior after being parked and vehicle was stationary. first time repair was made under cpo warranty with ~39k miles. second repair made for $750 (cpo warranty had expired). second regulator failed after less than 10k miles, and only 22 months, from first failure. bmw service technician says "it happens." bmw does not honor their 2-yr parts warranty for parts replaced when repair is done under warranty (and thence expired). the window regulator(s) appear to be a defective design to break so frequently. the actual failure appears to be with the "window regulator driving dog"(about a $10 part if purchased online) and a tiny plastic piece breaks off.