Phil-t is on the right track, I know on my (2013 Winnebago Vista 30t ) every once and awhile I have to sync the motors on each side of the slid (mine is also Lippert 2 tracks per side, motor with gear is located at the top and a shaft runs to the bottom gear). That procedure is to run the slide all the way out then run it in 5 or 6 inches then run it back out (holding button down till the slide stops) then repeat a couple of times then attempt to close the slide. But again I would check my owners manual for your type of slide.