Since I've been testing the 1040 I've noticed two more oddities related to data.
1) Strava: In strava activities sync and are recorded. Even though the activity shows the mileage, the mileage isn't being registered for total miles ridden (miles this week, total this year etc). When I use the 830, this does not happen and it appears correctly. Is it possible that there is a data sync problem with 1040? This is confirmed across multiple activities so it isn't a single outlier. - I've reported this to Strava also. No response yet.
2) Garmin Connect: When completing activities with 1040 there is no data point logged for vo2max. I can see the HRM and PM data logged as expected, but it doesn't update vo2 if I use 1040. This also works just fine if I use 830.