Bumping because I have a similar problem, albeit with an Edge 500. It's managed to corrupt my file from yesterday's Snow Roads - I loaded it into Garmin Connect as usual, and it's displaying correctly, but when it syncs with Strava the activity is truncated (147 miles instead of 187). Uploading the fit file directly to Strava also doesn't work (I get an error message). I tried exporting a fit file from Garmin Connect, but I get a bizarre 35-second activity in which I apparently rode 26,000 miles. Which would be nice, but it's not quite right.
I've tried the fit file tools and the Dutch websites but neither worked. Does anyone have any ideas?