Gee ya got me on that one, it is NOT completely gravity fed, I confess, sorry for being so misleading /snark off
Really though, thanks for taking the time to respond.
Now from what I can tell you are saying something about a level that is obtained in the transfer pump station (sump pump? not sure what to call it, please don't hit me) that is somehow drawing from the toilet because it is too high. Hmm, I have never opened that up since it's sealed and there is only one pipe coming out of it that I can see, but maybe there is a float in there and if it's like the ones in a Ford PU, they can get a hole in them and they end up sinking giving a bad reading or in this case triggering the pump later than it should because the level is too high rising above the vent... is that what you mean? It sounds plausible but I have to see a drawing to get a better idea of how to combat the problem.
I'm going to go take a good look at it and get a name and maybe find a septic forum and try to figure out where they vent it and if there's a float, yada, yada, yada. Maybe I can blow the vent out if the problem ends up being a clog?
Thanks for your help!