Manual import rides incorrect

There have been a couple of times now where I did an outdoor ride and Trainerroad did not get the ride synced from Strava. When I do a manual import of the ride (based on either the .fit or .gpx file) the average speed has been off by 2km/h and there has been a small discrepancy in the total distance of the ride compared to both the Strava report and the metrics on my Wahoo Roam.

As was the case yesterday, I deleted the manual import, disabled and then re-enabled Strava synch and the ride came through with the correct stats.

Any ideas why this would be?