This is what I do (in german though!): - downloading a gpx file to my Edge - navigate -> Course ("Strecke") -> saved Courses ("gespeicherte Strecken") -> select my new gpx file - press "Go"
This is what happens: - works just fine - on the map page map tiles will be loaded straigth away, so my Position/triangle is Always shown on a map
BUT: once I press start (start the timer for recording my Training session), map tile will not be loaded any more, my Position/triangle is not shown on the map anymore. It just Shows a blank screen with the triangle/my Position on it?
I have never heard of anything like that. If it was mine, I'd check it was up to date then do a full reset. I usually save the settings.fit file first, do the reset, then put the settings.fit files in the newfiles folder on the 820. This will keep all your activity profile setups etc so you don't have to redo all the screens etc. There is a possibility that the problem is with the settings.fit file, so try the 820 after the reset but before putting back your saved settings.fit file.
I'm not sure what's happening for you but you might try reducing the amount of map detail. If you're in a busy area, like a city, more detail can slow it down. Menu, Settings, Activity profile, (profile), Navigation, Map, Map Detail,... I use Normal in most areas.
