Black Tank reading 1/2 but appears full

[simtec820]

When i tried to fill my black tank up via a hose in the toilet, when water started to about come out of the toilet, the tank sensor panel only showed 1/2 full. I emptied the tank and performed the process a second time with the same results.
I know I've had those readings show up correctly through regular usage on the panel so I'm wondering what's going on. Could filling it through the toilet be causing a "false full" somehow? That's a lot of gallons to be missing somehow.
I have a Tiffin Allegro Bay 34XB 2009.

On a side note, can you fill the tank with the black flush hose as long as you monitor the panel? Just curious since the side panel says to always have the valve open (drain) when using it.

[450Donn]

Tank sensors are all notoriously inaccurate.
Do you know the tank size? If you do I would suggest you might want to do a tank check. With an empty tank dump 5 gallons of water through the toilet one at a time until its full. Counting the number of buckets you dumped in should nearly equal what you understand as tank capacity. If you have access to a bore scope you might also scope the tank checking for dreaded poo pile.
After a couple of years I gwve up and never looked at my tank sensors. Instead I learned how long I couls go before dumping and only dumped then. Which usually worked out to weekly.

[Goodspike]

My guess would be a wire came off a sensor or was otherwise damaged.