Black tank scrubber problem

I was using the scrubbers last time I dumped. I noticed not as much water was coming out of the tank as what I think is going in. We had very good water pressure at the campground so the flow should be much greater than I saw. No water was on the ground under the camper. I took my knife and punched a couple of holes in the belly pan, the under belly covering, and no water came out. i did notice some water leaking from the shower where the shower stand meets the linoleum floor in the bath area. I looked under the shower floor and the plywood was not wet. There was, however, water on the shelf behind the the dump valves. That was enough to use a towel to dry it up. Anyone have an idea what is going on?

thanks
Gary