Not only with the drain problem, but also parts & service info for our potty fresh water valve leak.
gray water problem:
We confirmed gray water plumbing is open between sinks & shower, but still looking for where it goes from there. The owner's manual shows 2 external sewer drain valves (owner's manual page 39, figure 10). Ours looks like the attached.
Anyone who has a rig configured like this, please let us know how it works.