Sometimes when I finish an activity and sync it via Garmin Connect I don't get all segment achievements until I use the "Refresh Activity Achievements" function on Strava Web. But how I am supposed to even know that segment achievements are incomplete. I can only see that if I look at every segment individually.
For example, here is the same activity after I initially uploaded it (as seen about 1 hour later after the upload) vs. after refreshing the activity achievements: