Based on my experience - bad readings for the fresh water tank were due to being out of "level." See that your camper is level and check the water level on the panel - this might help.
We also found that the fresh water tank "pickup" line was about 1" above the bottom of the tank. This left a lot of water in the tank - when the pump was still trying to pull water. We relocated the water pickup line to the bottom of the tank, where the drain valve is located. This allowed us to pull every last drop from the water tank before being dry.