Activity map is missing when synchronizing with Strava

The activity map is present in Garmin Connect but is not transmitted to the Strava application.

I would like to point out that this problem only occurs when the activity takes place with a home trainer and using an old route that has already been recorded.

If I use the .gpx file from garmin connect and import it into Strava then the map is displayed correctly. 

This is totally incomprehensible !

Thanks for all the help.

Laurent