Starting a new thread on this as previous ones are quite old now.
Android Explore has not been syncing my watch data to Activities for some time, occasionally it does and recently it has created two identical synced activities.
It may have something to do with Explore running in the background but I don't recall this issue last year.
I can see that some specific watches have had difficulties. I use an Instinct.
No problems syncing activities to Connect and to Strava.