I noticed late this summer that my Sense and Dispense system was using a lot of acid but rather than checking the pH level with my tester (lesson learned), I depended on the reading from my Pro Logic system which has been showing from 10-13 ppm. Finally, got my chem back in balance but now have a malfunctioning probe. Do these need to be cleaned from time to time or is it a sign of a bad probe, which are not cheap at all? This equipment is a little over three years old.