Yep, you're right, it is a very common problem with several suggestions on how to fix. I would recommend putting a solution of Dawn and Borax with a couple of bags of ice and then driving your rig (the more curves the better) several miles.
It worked for mine and now I always use the solution after dumping the tanks and before driving home. Hope that helps
There is also a thread on here about replacing the sensors with a new type that is less likely to fail.
Welcome to the wonderful world of camping