That's a pretty good guess. Quite why it wouldn't re-route me to the next known shaping point which was about a mile away in the town and from there to the rest of the route, I am not sure. I have a nagging feeling that the modern devices - like the Nav V and its Garmin equivalent - like to have a few waypoints built into custom routes, as opposed to just lots of shaping points. With my A to B route there was only two waypoints, the departure hotel and the arrival hotel, separated only by my custom made route consisting entirely of shaping points.
The odd thing then is thst my two friends also made recalculations; sometimes their devices made them perfectly, sometimes they didn't.
It appears from what i can glean from the web that if a point (waypoint,via,shaping) is missed (not ridden through,bypassed, ignored) as you ride your route, and you then come to a point where you need to or are asked if you want to recalculate, say at a road closure or you stray off route, the sat nav will then take you back to the last missed point, and then re route you from there using its pre set preferences, you may have missed several points, what occurs then i do not know, it may go back to each one, until it has routed through them all, and then begin to take you to your destination, if you have not missed any points on your route, or you have actually told the satnav to skip the point or points, it should in theory take you to the next available point going forwards. as i say i dont know and can not test it due to not having the latest device.
With reference to to the detour functions,
If you are on a route and come across a road closure blockage or whatever. you can use the detour function tap 3 bars in the lower RH corner select Change route - Detour then select preferred option, this is for the 590 but may apply to other units.
Skipping a point in your route
If you pass a waypoint and the device did not announce it (no route directions given until you either go back to it or skip it), you can skip it by (in the map view) tap 3 bars in the lower RH corner select skip, it will then direct you to the next waypoint/shaping point. This prevents the device attempting to route you back to the missed point.
The txt below could be very helpfull for some as it will show changes to a route and also alow you to see what has altered and where, this is from another source.
Tracks (tracks are a representation of intended route that never alters)
Before you set off on your route It's worth laying a track for reference.
Track settings go to Apps - Tracks select track (that's been sent from Basecamp). (To Convert a route to a track in Basecamp on your PC right click on the route's name in the left hand listing and select "Create Track from (Selected) Route) tap wrench icon tap "Show on Map" tap "select colour" I use black.
What you'll see on the Map page when the route is activated is the magenta route path of your Trip with a black line in the middle that is the track (if your GPS is capable) so whenever the device re-calculates (auto or you click yes if prompted) you will see how and where it changes your route.
You will notice if the device re-calculates off the track, If you ignore this and stay on the track (black line), not on the Magenta route, there will be no route directions given until you re-enter the magenta route. Actually route directions are only given on the magenta regardless.
In Tracks - Wrench Icon You can alsouse the "Convert to Trip" option if all you have is a track. This is an excellent feature for those of us that travel on roads or trails that may not be on the map. Converting the Track will create a new Trip (route) of the same name in the Trip Planner that is usually a complete representation of the original Track. Now when I want to navigate the Track I go to the Trip Planner and select my "converted-track" and press GO.
I used the theme editor at the following address to modify the theme on the unit and double the width of the track. Makes it much easier to see.
http://www.javawa.nl/zumocolors.html
As i have said this information is only what i have picked up, i can not prove any of it, and it may be all rubbish but those of you who have the newer devices could at least try and see if it is correct, and pass on your opinions.
This may go some way to explain why you are getting the weird route after recalculation,