That looks like the shower in our RV too. Ours had lots of leaks in similar areas. I ended up disassembling the shower and re-assembling the surround. If I remember properly, on ours the big issue was missing silicone at the bottom plate, especially in the bends where it's notched out.
(went out to the RV to look and remind myself what I'd done) I had to do the disassembly to gain access to that area to add the silicone. The vertical sections channel the water down to the bottom tray and it supposed to flow back into the shower. On mine it was able to go under the tray at those corners and the left-wall connection.
