We had a very similar situation (TWICE) where the slide catastrophically failed to extend within the first 6 months of owning it. It only went out about 2" each time and STOPPED. After the second time (we were on vacation in Florida after driving from Virginia) I called the factory and TOLD them I was bringing the rig in for repairs. They got me in the next month and found that not only was one of the two roller sets NOT aligned but the two were not enough to handle the 30' of slide.
One of their top techs told me that he put in a 3rd roller and track to ease the amount of weight and stress. It's worked fine since and I believe that Thor realized the engineering flaw and has subsequently been building that large slide with 3 rollers sets and tracks.
Good luck as I've also discovered (almost every trip out is a new 'surprise') that this model is an electrical nightmare.