To the OP, if we are understanding you right, you can get the servos to work in the flap channel if they are plugged in directly, and any of your servos will work with a Y harness in the aileron channel? Have you tried just plugging the known good Y harness and servos you are using for ailerons into the flap channel? That will tell you if there is an issue with your receiver or the settings in your transmitter.