Hi Guys , Its likely the regulator. My pass. side went at 39k and the drivers just went at 50k. These regulators are built pretty flimsy, the bicycle cable they use (not stainless) to transmit motion corrodes and the strands break one by one until it either jams or finally breaks.
I removed my regulators and had them restrung with S.S. cable at a fraction of what the general wanted (200 + $ for complete assy when only cables are bad). Save the bad regulators for rebuilding then you wont have to remove door panels twice. Not sure if they will give you the old regulator on warranty repair but try.