Now you've got it !
There's absolutely nothing you could have done about this situation - nothing that would have made sense at the time anyway.
But there are things you can do to help to deal with the the gotchas that the Zumo can throw up. Its largely to do with making sure you plan routes in a particular way and use the various types of point to best advantage. Get it right (and it isn't difficult) and you will be able to keep your hands off the Zumo when riding and either follow or ignore the instructions and know exactly what the Zumo will do as a result.
Give me a day or two, and I'll put some simple, jargon free, easy to follow, illustrated notes for you.
Is Linville local to you ? It will make more sense if I can create a local example for you to go out and try.
Don't bother about the screen shot - sorry the request gave you a headache. @sussamb provided me with the confirmation that there was no road on the Garmin maps, which was what I needed to see.