My black tank sensors work almost all of the time. My grey sensors will often show 1/3 when empty, but the rest of the lights have no issues.
I use the GEO method, and use my tank rinser to fill it up all the way before dumping. If I have time, I will fill it up again, dump and rinse while dumping. Continue rinsing until clean. Put 5 gallons and the GEO mix in.
I do use the toilet while it's sitting in my driveway, maybe sitting for months at a time. I repeat my dumping procedure right before leaving to a campsite and let the clean mix slosh around while driving.
Maybe overkill, but I like to see the lights work. On a possibly related note, I never smell anything bad in my trailer at all.. While dumping, flushing, while sitting in 100*+ weather, nothing. Possibly due to my being anal (pun intended) about my dumping procedure.
2017 Jayco Jay Feather 25BH
2004 Nissan Titan