Sensor Repair
[RonS] I have the same problem, and I think all do if the unit is over a couple years old. I am waiting for others to reply to your post so I can try what they offer. I have added a number of cleaners but nothing worked so far. I have been told, but not yet given it a shot is to after flushing tank add about three gallons water then dump down a couple bags of ice cubes into the toilet and drive down a bumpy road. The ice bouncing around is to clean up the inside of the sensors by knocking off all the crud. Then they melt and all is well.
Ron