this is a strange bug in NWC, why should NWC reset the current cursor position when switching tabs in the 'Page Setup' dialog???
I don't think you will see this happen if you click just about any of the tabs. If you click the "Options" tab it will scroll, as well as if you click "Contents" tab once, and then one of the other tabs (except "Options") it will also scroll.
Clicking "Margins", "Fonts" or "Preview" tabs won't give this effect; at least not on my machine.
But I agree, it's annoying behaviour.