Hey Keith Massie,
Feel free to reach out at jwhitney@esri.com and we can discuss more.
I believe you're running into a known issue where the map scales are getting set based on basemap visibility range. This can effect how far you can zoom in or out. We're working on a better long term solution but in the meantime let's see if we can get the map behaving as you'd like.
Can you describe (maybe an image) of how the basemap is set up? If look at the last layer in your TOC, what type of layer is it and what are the visibility ranges set to for that layer? My guess is the layer either has a min scale set on the layer OR the layer (maybe a TPK / VTPK) has an internal min scale that is restricting you from zooming out further in Navigator. You can try setting the min scale to a higher number (1:200,000) and this should enable you to zoom out further.
Joel