HELP?!? First time flushing tanks-not going well.

[mrs_sealcoat]

First time fifth wheel owner, but previously a 2013 Sprinter TT-so I thought I had a good handle on tank flushing with Keystones. We have a 2019 High Country 385BR . This was our first week using it and I just went to flush and clean out the tanks. Nothing worked right and I’ll let you guess what happened when I attempted to open the safety cover and attach the sewer hose. 🤦🏼*♀️

1st issue: The black tank only has a lever in the "convenience center", not above the actual exhaust line. (The gray tank has one in the convenience center AND above the actual gray exhaust line). The problem- even when the black lever is in the closed position inside the convenience center, it still has a steady but light stream of fluid coming out of it.

2nd issue: We're seasonal, so I don't leave the water on when I'm not there. But when I turned the fresh water on for the camper today from the post, it started pouring out of a line underneath the camper in the rear corner. There was a valve with a knob there, but in all the times we've used the camper in the last week, nothing has come out of that.

Any ideas where to begin here??? I've attached pictures for reference.
Thanks so much!!