Garmin really should stop advertising that they support Apple Health or find someone who knows how to code the Apple Health API because right now, Garmin Connect is just corrupting Apple Health data.
1. Garmin Connect (GC) is writing a corrupt "resting heart rate" record even for a biking computer. The record SHOULD have a sampling start/stop timestamp, but it is always tagged at precisely midnight. This is incorrect. Also, why would a biking event create a "resting heart rate" when it is typically done while sleeping. This is skewing data that is being sent to my medical records.
2. Why does GC re-send workout activities from almost a week ago? Today, I did a 3.5km walk and when I synched it to GC, it pushed all my workouts for the past week into Apple Health. The Apple Health workout data shows refreshed timestamps. If someone at Garmin knew anything about Apple Health, you'd know that they have introduced additional attributes to the workout data, even that which was imported. Every time that that GC resends the workouts, it destroys the additional data. As a lead developer, selecting which workouts to send to an API is basic development that any new programmer should be able to know how to do.
None of these fixes are hard and would increase the value of Garmin Connect, but Garmin has to be serious with their app development, which they obviously are not.