Single hydraulic ram drives the slide out open/close.
When piston moves in/out it drives a gear that engages rack by the ram as the gear turns a cross shaft drives the slave gear on opposite side which drives that rail.
Cross shaft is bolted at both gear packs.....possible broken bolt
Slave gear pack could also have broken teeth so that it doesn't engage rail.
In order to check which is the problem you will have to open underbelly covering
Cut a three sided window directly under rail about a foot inside frame.
Cut window so that non cut side is forward then bend it down
I had to replace gear drive assembly on piston end AND replace broken bolt on cross bar n slave side .....so 2 windows needed
After repair just close p windows using eternabond tape.
S/B a Lippert System........pg. 28
LINK