Is this the combined shower / toilet?
We found it a good idea to slightly adjust the level so the shower was able to drain easily....towards the rear, I think.
I'm assuming you direct the shower head away from the area as much as possible?
If all the above is done and it still leaks, it's gotta be the sealant!
(I just read it again....gap above the frame to the bed area.....sounds very high for a Jayco shower!)
Good luck with it....I'd be checking the seals and making sure no water is directed at that area. If you get water where it's not designed to go, you'll have problems in the future.