Welcome to the forum. Good luck w/ your new boat.
FYI, the Vacuflush waste tank is black water not grey water. Grey water is from showers and washing machines, not from toilets. The 380DA grey water tank is under the salon floor, for the shower, the head floor drain and the two AC condensation drains, w/ automatic overboard discharge.
The typical problem w/ the Vacuflush level sensors is those sliding float switches becoming stuck because of crud accumulation.
On my boat I snipped that wiring harness and properly installed a nice inline connector. Now I just unscrew and remove that switch level sensor assembly for remote cleaning.
Removal of that sensor assembly also creates a large opening to the tank interior. I use that to permit scrubbing the interior tank walls. The tank is first properly evacuated, w/ the deck plate pumpout, or the macerator pumpout, then the empty tank is scrubbed w/ a looong brush and cleaning agents.
This permits a visual inspection through the side walls of the level, not only needing to use the level sensors.