I use a 910xt with garmin express/connect.
This problem has been going on for maybe a week. Today I rode my bike. In garmin connect, it shows 18 bike rides for today. That information is then sent to TrainingPeaks. I'm constantly deleting activities from my TP log. It isn't just bikes either. I get multiple upload for runs and swims as well. Just today, I've had to delete a total of 36 activities.
I've never had this problem until about a week ago.