Hoping someone can point me in the right direction. All of a sudden the rear wiper appears to stop working. Upon further inspection, the circular doughnut shaped "cap" the wiping arm comes up from the glass window is loose. The motor is fine, it will rotate the wiper the regular radius for 1 pass, maybe 2....but then it will rotate further left and continue making it's semi-circular wiping patter until it in 1-2 wipes rotates further left until it is wiping down near the rear license plate basically upside down. I assume there is some stopping mechanism to tell it to start here, and that's loose. Before I dig in, any suggestions?