The reset is happening because the screen update time is long enough to trip t0eh watchdog timer in Mach. It happens on slower machines and large screen sets like the NFS wizards. You can turn off the 'use watchdog' in the config page, or get a faster machine.
Thats how the wizards are programmed, always going through the material select and tool select. No real way to change that. For a single screen wizard the "run last wizard" button is more useful.
The Zstart or Ztop issue is one tha tis oftem discussed, but since the current way it works is burried in many screens its just to big a change to make. It would impact every screen of the set.