If you save(export) a list to a gpx file and than import the same file into Basecamp almost all icons get altered...
Same thing happen with Explore's exported kml files (once Basecamp doesn't open Explore gpx files...).
The only way I found to keep the icons is by sending them directly to the device using Basecamp. But even though not all icons keep the same when viewed in the Fenix 5x. I had to find which ones doesn't get changed.
Is it a Basecamp problem?