1.5 years ago, I had a leak underneath the shower in my Vegas. It actually dripped through floor cutout onto spring shackle. Access was panel with 4 screws. Turned out nut on shower strainer has loosened (I am 240). I added a rubber fernco connector on top of it with hose clamps. No more issues. I did have to remove strainer and reputty to get enough clearance to use coupling. All this beemingly standing on my head.
I cannot speak to Miramar, but there is likely a P=trap between shower and gray tank or you would get odor back from tank.
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