No, that Whale pump is about the best you can get. I check for vacuum
leaks between the tank and the pump. With all the flapper valves in
the Whale, it's hard to imagine them failing all at once. Are you
using cheap, single ply toilet paper in there? Also make sure nobody
is throwing anything else down there. If the valves are indeed being
held open, it's by something that shouldn't be in the tank to begin
with. Whatever that is would crud up a macerator as well.