A quick google has found a manual for that controller - http://www.leetro.com/english/down/p...%20En-V1.3.pdf

By the look of fit, the manual example wiring diagram shows the water protection (pin 3 on the input connector) as just being connected to ground. I'm guessing Redsail have added some kind of switch (low water level?) somewhere. It should just be a case of following wiring, to see what has been connected. Or maybe first add a temporary jumper wire at the connector to see if the fault clears, before investigating what the real problem is.