GPS Tracking Issues?

[adamwri]

Seem to be getting some issues with my new Garmin 810 when uploading to Garmin Connect/Strava. The biggest problem appears to be distance calculations. What should look like #1 typically comes out closer to #2, despite the routing tracking the same route and me actually cycling the same route to/from. I'm expecting 15.4-15.7km total distance.

1. 1: https://www.strava.com/activities/389942352
2. 2: https://www.strava.com/activities/407585207

Has anyone seen anything similar before?