Black tank gauge shows 2/3 when empty

[The Cramblersons]

Recently, my black tank gauge on the control panel is showing 2/3 full immediately after I dump. And then it goes to full after just a day or so of use. The last time I emptied was with a pump truck here in the Keys since the park does not have sewer hookups.
Are these gauges in the tanks capacitance or float types? If it was a float showing 2/3 full when empty, I would think it was just a float stuck. But then it increases to full fairly quickly, something a float probably wouldn't do until the tank contents caught up t it's stuck position and lifted it further.
Any ideas for how to troubleshoot, clear or reset the false reading is appreciated.

2016 Voltage 3305

[lcv800]

Mine do the same thing on both my greys and blacks (blacks worse than grey). Sometimes when I aggressively flush, the read somewhat accurately. I think a lot RV'ers have upgraded to See Level, which I guess is better than the factory gauges. FYI, they work off electrical current.
Rusty

[thompwil]

They are capacitance type so it would seem, discrete points of contact for each level. It only takes a little "stuff/paper" sticking to give a false reading. I'm actually doing a "maintenance cleaning" today while driving to Ocean City. Ten gallons of Simple Green water solution sloshing during the drive. I'll dump when we get there.

[The Cramblersons]

Thanks, folks. Capacitance are great, until they get gummed up. And by "gum", I mean....

I'll try the cleaning approach you recommend on my next move.

[wildwest450]

Never seen a stock rv tank gauge that was accurate. It's easy to tell when the black tank is full and the gray is full when the shower has water on the floor.

[thompwil]

There may be better stuff to use to clean..?.. I just had the Simple Green on hand. I've used Pine Sol in the past too.

[DesertRat]

RV tank gauges are about as accurate as a two year old throwing a ball.
When gray water is sitting in your shower & you can see what you just flushed down the toilet the tanks are full.