Basecamp reverts to Birdseye - track created with OS map

1. I create a track using OS map using Basecamp

2. I use Basecamp to convert it to be a route

3. Upload it to my Garmin Montana 680

4. It looks fine on OS map on my G M 680

5. Go back to Basecamp and open the route again

6. Now it will only show in Birdseye and not on OS map

(this is an offroad hiking route made by manually dot for dot...)