This was going around the forums about 3-4 years ago. The same thing was happening to a lot of coaches in the 2007-8 range. We had a 2007 Thor product at that time, and by the time we got rid of it, the seats looked like they had a disease. As stated, Thor furnished an inferior product to Flexsteel, so Flexsteel bowed out of any responsibility. From what I remember, Thor didn't step up either nor was it only Thor products that had the problem.
Interesting to note that we bought our 2007 in 2012 when it was 5 years old, and there were no signs of any problem. Within 6 months of use, we noticed the problem starting, and once started, the seats quickly deteriorated. You appear to be in the same window of time.
Hope you get some help, but I wouldn't hold my breath. You might have to just suck it up and get them replaced on your dime....frustrating, I know.
Gene, Gayle, & Oliver
2006 Holiday Rambler Endeavor 40 PDQ/2012 Honda CRV