Checked the trailer shower today and I think I found the source of the shower leak.
A VERY crude picture but..........on wall "A" where the panel meets the shower pan, there is a thin bead of silicone but there is a section where the silicone separated from the pan and if I push on the wall ever so slightly, a crack appears, so I filled that area with quick dry 3M 4200 marine adhesive. I also built it up so that the shallow channel (which is higher than the actual shower pan) that was there will not allow water to flow toward the curtain. I also cut down a small shower dam, deflector, etc. and again used 3M 4200 to hold it in place at the shower curtain location.
Walls B, C have a molding that is on the wall and goes over the shower pan lip which looks like it allows water hitting the wall to fall into the pan, so why wasn't this installed on the other walls?
Wall D had the same issue as wall A but without any wall separation so built up the shallow channel with clear silicone and installed a much smaller dam, deflector there.
I did inspect the hoses for the shower knobs as they are easily accessible from under the vanity. I was able to put another quarter turn on the connectors just using my hand.
I hope that's the end of it.