I have an intellichem with my 10,000 gallon salt water pool. For the most part it works wonderfully, without any problems. However, I've noticed over the past few months, approximately once per month, the ORP drops from 650 to around 500 ish. Then the salt cell with produce chlorine for about 2-3 days @ 12 hours per day. I have let it run 24 hrs/day to see if it brought the ORP back up. One the day that I reach 650, or within a couple days, I've had the water tested and had a chlorine level of 15 ppm. I used to notice a sharp increase in ORP when I would shock with Fresh n Clear, non-chlorine shock. However, I haven't seen that spike recently. Probes are all cleaned monthly, filters cleaned, and Salt Cell cleaned as required. Any thoughts?