Thank you to everyone who responded. I am going to try adding Happy Camper to black tank, fill with fresh water, and let stay for several hours while we're off seeing the sites. If that doesn't work, I will try the ice cube solution. And if still no luck, I will live with it. For 8 years in my old trailer, I never had sensors, and I had no problems. It just irks me when these problems pop up in a fairly new RV (2018).
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