The sensors are worthless, as I said before ice cubes, magic mixtures, over priced sensor cleaners all might help til the next tank full. I go by the sound when flushing to determine when to dump or do it weekly, forget the POS sensors.
I do add a healthy squirt of the dollar store liquid dish soap or liquid laundry detergent in about 5 gallons of water while traveling. As far as ice cubes, in my opinion, unless you dump lots of bags (like 5-6 10lb bags) of ice & took off immediately the ice would melt long before it would slosh around enough to do any good.
Danny & Linda
Sold our '13 Thor Redwood 36 FB
Currently RV & truckless