We tried all the tricks on our Pod to make the gauge work; filling the tank with a heavy, bubbly dose of Dawn; driving on NV dirt roads with ice in the tank; repeated wanding, and super solutions of tank cleaner. I finally got the gauge to work.... for about 1 trip.
And we never used the tank for #2 nor did we put paper into it. Those button sensors are utterly worthless. Now, for our new trailer, we follow the practice of no paper and no #2, unless it cannot be avoided and we never believe the level indicator. Just keeping a kind of running guess about how much you've put into it is going to be the best you can get, unless you get one of those really expensive tank monitoring systems, that may or may not work. I call it the Zen of tank maintenance.