It shouldn't try to settle if you have no dither set and for me at least, I have never seen that problem. Are you sure that you are turning dither off? If you change it in the equipment profile while you have the profile loaded, the change won't go into effect until the profile is loaded again. A log might be helpful. However, in the meantime, there is an easy fix. If you don't intend to dither, then just don't connect to PHD2 in SGP. Select "None" for autoguider and start PHD2 separately. It will happily guide away while SP snaps frames.
Tim