Just guessing here, ah you said you used a Y on the flaps and I would bet you used a reversing Y as it is often required with flaps on some of these arfs.

Its my bet that this Y is the root of your problem either the connection corrosion Rodney and Gray Beard suggested or something more heinous. I am not an electronics type but I have found a number of cheapie reversing Y's to cause problems.

John