Does positioning the diverter in either the tub or shower position solve the problem? A diverter is not designed to be operated in the "between" position. It is a diverter; not a throttling valve. When it is in the "between" posiiton it restricts the flow and the energy from the pressure has to be dissipated. That will make noise.
When water is flowing and you shut it off quickly, the kinetic energy in the water moving in the pipes must be dissipated. That can make a noise, just as it does when you drop a rock on the floor. The energy is about the same as dropping a half gallon bucket of water from about 1 foot. You would expect that to make a noise.
If you want silence, then you need to find a way to dissipate the energy slowly and without causing the pipes to shake.