I had a new motor put in the rear passenger door and I had the same grinding. I popped the door panel. Found the installed left the speaker wires in the path of the window. I moved the wires back to there spot, loaded the tracks up with lithium grease and it's super quiet now.

The tracks have no grease from the factory, and maybe they were designed that way, but they need them. PM me with your email and I will send you the door removal .pdfs from the manual.