2 concerns: Our fresh water indicator light always reads E when we know it is full. Our other tanks show 1/3 even after dumping. We treated the grey/black tanks with suggested stuff from camping world (pour in/ fill tank/drive around/empty...). I have heard the "take a 20 lb bag of ice and pour into tanks with some water and drive around suggestion. A service tech at Camping World warned that we could damage sensors that way. Any other help out there?