Try opening the gpx file in something like notepad. It’s really only text. You could maybe check how much content it has compared to one of your own.
I confess I’ve had this happen to me in the past when sharing a route by bluetooth and if I recall correctly, we fixed it by changing the other gps mode to driving and recalculating before changing back to bike. To be honest, if you are following a route built in basecamp rather than letting the Nav do it's thing, the vehicle of choice is not relevant.
Hello Shakey, I'm not sure what you are getting at. Everything I am doing is contained within Basecamp and using existing routes that work fine in 2018 maps and transfer OK to the Nav. My issue relates to updating the maps in Basecamp, those routes that worked on the previous version of maps do not then display correctly in the new version of maps, they show as direct lines. I have deleted the new maps from Basecamp in an attempt to do a reinstall to see if it worked after a reinstall. I now cannot update the maps in Basecamp, despite reinstalling Basecamp and Express.