I have a D120 and resistive fuel sender. I have the sensor set to resistive (#1) in the system. I have tried 2 different resistive fuel senders. Senders are compatible with Dynon. Both times the calibration failed. The reading stay at a certain value for about 10 gallons before the sensor value will increase. Then it will stay at the next value for about 10 gallons. It always tells me it didn't sense that 2 gallons were added, so I hit the yes button. I am at a loss of what to try next. Any ideas.