The Lippert system that PC is using does not have a manual override. I hate to say this but there are other 3100 models that are having slide issues as well. I have the system in my 2552 which I believe is the first year for PC. Mine works well so far, but I watch it closely when opening and closing. It sounds to me like you have a gear that is missing some teeth. This happens when the side binds or people are sitting in the slide when its being opened or closed. I have a pretty good understanding of how the thing works as I was very curious when i got my PC and did a bunch of research just in case I had issues. The only thing you can do is go to the controller and unplug the motors which release the brakes in the motors and you can manually push the slide back in... Thats what they say but if its bound up, not sure what happens... Take a close look at your tracks on the side of the slide and see if you notice any damage to them, that will give you a clue as to where the problematic gear is . There is a gear for each track, and they are joined by a shaft and driven by a motor. So you have 2 motors one on each side. Each motor is driving 2 gears one for each track. There are gibs that help keep everything in alignment. There are also some Teflon rollers under the slide for support.
I am not sure if you are aware and have been holding the button to open or close the slide 5 seconds after the slide stops. This is recommended by Lippert to help keep the motors in sync. If you allow them to get out of sync the controller will be flashing a red LED light not sure which one but it tells you on the controller. They also say you should be lubricating everything annually, which i have done and its a real pain. Rather get a root canal then do it again, because of how the wall is shaped and how far back everything is set.
I hate to say it but it doesn't sound very good.... Best of luck and I would be interested to hear how it works out for you.
Lance
Forgot to add that if the motors get out of sync the slide binds and teeth on the gears end-up getting broken...