The culprit in general is dirty tank walls where fluid holding crud builds up and fools the sensors into thinking there is fluid in the tank.
Whatever you can do to clean the walls may help.
I have tried everything recommended over the years - ice, TSP, various solutions, Happy Camper, etc - and nothing worked.
Some things that do work for weekend warriors don't work for full timers and that may be why some methods work for some people and not for others.
I know I have to dump the black tank every 10 days so I just mark the calendar and dump according to it.