Sbus zoom

Ok i have the zoom set to channel 1 (the camera is on a different radio than the copter). This way i can zoom in and out with my left and control the gimbal with my right. I though the zoom was a rocker type but it acting weird. I push the left sick up and it starts to zoom out and then it stays and slowing goes back in. if i return the stick to center it zooms in again. Is there other settings in the camera to fix this?

any help would be greatly appreciated

maybe this depends on the lens. I have a Olympus 14-42 EZ lens and after steering up (depending on how much) the lens zoom up into extreme. The same when I press down, it zooms out into extreme at one of three different speeds. I cannot get it to zoom to anything between 14 and 42 mm, so it should not zoom when centered. Maybe the centre is not aligned very good?