As you probably know, the sensors on all the tanks are finicky and prone to giving false readings because "stuff" gets hung up on them. If you use a wand or your rig has a built in spray cleaner for the tank does it ever give you something less than full?
Also, on our TT I found that the wiring on the grey tank was done incorrectly and it would go from 1/3 full to full. I checked the color & sequence of the wires on the black tank (which worked correctly) and matched the sequence of the grey tank wires to the black - problem solved for our grey tank.
I just want to be outside!!!
'17 Salem Cruise Lite 210RBXL
'11 F150 5.0
Two shedding mutts