My seal on my previous Travel trailer did the same thing. It has to do with the cheap rubber used and the Florida sun. It did this even though I religiously lubricated it with slide out seal lubricant. I was doing just that when it tore apart wiping it down previous to application right before selling it. I called a mobile RV guy who ordered the part and installed it. Found the guy on Craigslist.
Experience without good judgment is worthless; good judgment without experience is still good judgment!
2018 RAM 3500 Big Horn CTD
2018 Grand Design Reflection 303RLS