A few days ago the passenger side automatic slider started not opening or closing all the way with the push buttons. Whether the door is opened or closed, it stops in the same place about eight inches from full close. From there, we can open or close it freely by manual action. The automatic engage/lock works well when the door is at the fully closed position. I have checked the track and all appears clear. I have checked my Chilton's manual and don't see any troubleshooting tips and would rather not spring for a new motor if I don't have too; having been replaced in the warranty period, the current motor is probably not more than 20,000 miles old. I would appreciate any tips. Thanks!