One night, our Toto Toilet just kept running. I have a GMAX TSU18A in my tank. After reading the forums here it seemed to indicate that this model is not fixable and to buy a new one. After installing the new TSU18A, the same problem. The water won't stop. I have tried adjusting the height from the water line. According to instructions it needs to be within 1/4" from the overflow height. I've tried making it way below, or slightly above just to see what happens, and still the water will continue to run. Any ideas?