hello martyn, the trigger should have a 2 stage feel to it so needs adjustment by the screw on the base of the trigger blade.sounds like the screw is screwed too far out.this results in the trigger only being a single stage and the unpredictable feel to it.try turning the screw in a bit at a time and see what happens.i think the second stage should return by doing this.i haven't adjusted mine in a while so hope my memory serves me well.try it and let us know. atb