I have a 25 gallon lagoon that I use the 3155 osmolator for top off. I've had the top-off set up for about 4 months. Recently (last 2 weeks), I have this issue where the top off fills to the optical sensor and then shuts off. Then an hour or two later it will start filling again past the sensor forcing the manual switch to trip forcing the pump to stop and alarm to go off. I do have these two at a similar level but this issue has only recently begun happening. I've cleaned the optical sensor with soap and water. Any other things I can try?