Hello @hglotti 

Thanks for posting about this.

Can you confirm that the workouts that are not syncing contain GPS data?  Indoor workouts or activities that do not contain GPS information will not push to Strava from Samsung Health. 

Another thing to check:

Check and confirm that you are using the most recent version of Strava and you have updated Samsung Health to the latest versions.

If you're still having problems after that, please go ahead and do a manual disconnect/reconnect:  Disconnect Strava from Samsung Health. On the Samsung Health App, go to Menu (the 3 lines top left) > Settings (gear icon) > Connected Services. Tap Strava and confirm to Disconnect. Once disconnected, go ahead and reconnect by following the directions on Samsung Health and confirming your account information.

Please let me know if any of that helps.