Starting doing this a few weeks ago possibly after last update. Only changes distance (not speed or any other settings). I spoke to a 510 owner that was experiencing the same effect. Tried several times to sync using "Garmin Connect - Devices & Sync Status - Device Settings" which already claims to be in km's but not surprisingly nothing changes on the 810.
So only fix as of now is to go into the 810 settings (after each time it's been disconnected following a Garmin Connect upload) and change Distance setting to Metric. Not the end of the world but it's getting annoying. I guess most Garmin users are not metric.
