My camera shake script works in editor and web, but not iPhone

    var dir = wantpos-transform.localPosition;
bumpspeed+=dir;
transform.localPosition+=(bumpspeed*Time.deltaTime);
transform.localPosition=Vector3.Lerp(transform.localPosition,wantpos,smoother*Time.deltaTime);

I'm using this in Update to shake my camera. It works in the editor and in the web player, but on iPhone the camera doesn't move at all. I'm wondering if there is a precision problem, as the scale is pretty small. Does anyone know how I'd fix this?