I have a hot tub with a balboa system. I have had it and used it for years, I recently cleaned the tub and refilled, it was working fine until I accidentally overflowed the tub topping it off ( not the first time) ever since its been in EC mode, I know how to change it and I keep setting it to St mode but the system will not stay in ST mode. no matter how many times I flip thru the systems. I am at a loss.