@kylatin The warning doesn’t imply the activities have not been synced: if you see them in Suunto app on the phone after having synced via Bluetooth, then the activities have been synced but, for some reason, this didn’t trigger the “mark as synced” feature in the watch’s logbook that prevents the warning from being triggered.

Having said that the warning is just that - an annoyance - but doesn’t have any other consequence (because the watch’s memory is circular, so newer activities will always overwrite the old ones), it should still be avoided by sync via bluetooth. Is it possible by any chance that when syncing you had power saving on on the phone? I’ve had a friend with the same issue and apparently removing that before syncing on the phone solved it