Okay, so I feel like I've seen posts on this but couldn't find any browsing the first few pages or by the search bar.
So I've been testing Navigating a saved course. I tried some mountain bike trails a few weeks back and went off the course on purpose. I did get a off course warning but the 820 did not try to re-calculate to get me back on course. So on Saturday I loaded up a test course around my neighborhood and took several wrong turns. The Garmin just gave me an off course notice but again did not re-calculate. (although my position kept updating on the map which is contrary to what I've read here.)
I simply kept riding and when U joined back up to the course on the map, the navigation resumed. Is this how it's supposed to work? perhaps it would only re-calculate if you are navigating to a specific destination?