I had the same issue. The front thigh cushion (which is where the split is coming apart) is sewn to the front of the larger seat pad, ie a smaller cushion cover with seperate foam insert attached to a larger cushion cover with its likewise seperate foam insert That weak join, in our van at least, is almost directly over the couch base lead edge which provides a perfect pivot/stress point to ensure the 2 pads are very unlikely to stay together. Total design stupidity with inbuilt stress points.
Blackmans do Jayco's leather couches, but I believe they do the cloth in-house at the factory
I was lucky enough to have been living in the van so the cushions got a daily workout and the seams opened up during the warranty, so I had them all replaced. As luck would have it our original unattractive colours were discontinued, so Jayco replace the entire lounge (backrests as well) with our selection from the current colour range.
Many Jaycos have seat bases that are almost full cushion depth .... but mine aint one of them. I was going to rip the entire couch apart and rebuild it with a deeper seat base to better support the cushions, but that seemed a little extreme (even by my standards) so I extended the hinged plywood access flaps about 80mm overhanging past the base. Those extensions are not visible but give substantial support to the over hang of the cushions along that seam.
These are the new cushions, but they have the same fatal design flaw. The wing cushion end closest to the camera shows the cushion overhang, and the cushion joint seam almost directly over the base edge. Any pressure on the cushion edges tends to force the cushion edge at the seam down over the base, effectively trying to constantly rip open that seam
View attachment 60153
5mm thick sheets of MDF attached only to the hinged section of the seat base, when closed overhang the base around 80mm and supports almost the entire cushion over hang. Pressure on the area now mostly just compresses the cushion. The 5mm MDF doesn't interfere with the opening or functioning of the hatches at all, and I'm hoping the MDF will extend the service life of that seam
View attachment 60154