Van?s fuel level sender

Seeking help from the group....
I have recently finished and flown my new RV8 and I?m having strange indications from my left tank float fuel level sender. Sometimes it indicates correctly, but then it will suddenly go to zero, or some very low value. I know the tank is full, or nearly so when this happens. At first I thought the float was sticking, even though I was very careful when installing it. But then I thought, how could a float in a full tank suddenly sink to the bottom and stick there? I?m flying in smooth air at 1g and the indication ?sinks? to read zero. I have a G3X touch and I think it sends a 5v signal through the sensor wire to read resistance(?), so what could cause this indication? Before I go through the, not fun, job of scraping off proseal in the confined wing root area to remove the offending sender (I?m NOT removing my fuel tank), does anyone have suggestions for a possibly easier fix. Has anyone else experienced this indication?
Thanks

As the level changes shaply, it sounds like a wiring issue.

As you check the wiring, don?t forget to verify the sender case is really grounded. If not, run a separate ground lead to a wire with a ring connector under one of the sender screw heads.

Carl