I can't imagine why they would use two motors on that slide, or any slide less than 16 ft in length. Unnecessary cost and installation problems. I'm confident you have one electric motor, possibly driving a shaft with two gears if the slide is longer than about 8 ft. If one side moves while the the does not, the gear on that side has probably broken the pin that connects it to the drive shaft. However, bedroom slides typically have a direct drive and no gear shaft. The slide isn't big enough to need to two gear drives.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC