the gain or proportional (gain affects the built in gyro and the proportional controls motor output) will have nothing to do with the swash plate servo controls. that is purely a servo control issue. it does sound like the 4 in 1 is bad or the ccpm mixing software is screwed on the controller.

just to be sure, make sure all the servo connectors are plugged all the way in. check that the radio crystals are snug on both receiver and transmitter.