Your first issue might be a broken wire on the sensors for the fresh water tank.
The sensors in the black/gray water tanks gets gunked up and they don't work properly. There is a new type of sensor that is supposed to work better. I have purchased a set but not installed them yet. Horst Miracle Probes (now made by Valterra - not sure if they are available yet) use the same process (detecting the presence of liquids) as the existing probes but utilize a very different design (pictured below) - but they work with the existing meters - just remove the old probes (after draining tanks) and replace with these probes.