Avoiding controller "jump" when linking

Hello,

I am trying to learn to link a midi controller (simple M-audio Keystation 49) to FL. I have manage to write some simple python to control the 3 transport buttons and some other simple stuff. I am trying to figure out the override generic controller function. I have linked my only fader to the cut-off frequency och 2 different VST synths plus master volume in the mixer and saved a new template. All works fine when I open a new project and this test template. But how can I avoid the "jump" in the controlled target when I move the fader? What happens is this: Lets say I moved master volume to full volume and one of the cut-off frequencies to 0. When I focus the mixer again and move the fader, it jumps to zero.

Peter