Sewage valve stuck open

Well, the valve problem is not resolved but I made progress today. I got the auger and ran it down the toilet... and encountered no resistance. I ran the whole 20 feet down there and it didn't even feel like it hit soup. So I got curious and disconnected the drain pipe, filled up the toilet with a gallon of water, and let it go- then ran outside to see what came out. It was pure liquid, brown, but no lumps. By the time my husband got home I showed him what I was investigating, and we ran more loads of water down the toilet. We ran a garden hose inside the RV, hooked the drain pipe back up, and dumped about 12 toilet-fulls of water (not steady streams, I wanted to let loose waves of water for better force). Then I disconnected and ran a single gallon again, and presto, the water coming out was quite clear. And the gauge is down to the bottom third light. Now it is not so urgent- I know the flow is still okay, and I can start figuring out what to disassemble to find the exact problem. :)