Mapsource doesnt support correctly current City Navigator maps, see:
https://forums.garmin.com/showthread.php?32445-MapSource-Crashes-Frequently-with-CNNANT2013-30-maps
I created the route with another map and then switched to CN NA NT 2013.40 and found an area (N36.53959 W82.14231) where simply viewing the route crashed MS. That said it crashed when zooming from 0.3Mi to 0.2Mi.
Now I have a GDB file that can be used for testing I'll play with it and see what I discover.
Also crashing in MapSource 6.15.11 under Win2K although the error information has different details.
From this I'm guessing that new map feature(s), that is data, exists in newer maps at some locations and MapSource doesn't know how to deal with that data. A crash can occur when MS has to deal with that data either by viewing it (by zooming in), creating a route etc.
MapSource 6.13.7 crashes just like 6.16, even error messages look similar.