I am having a hard time keeping my Garmin Fenix connected to the Fairphone. Bluetooth connection is kind of stable - unless the phone is out of reach. Comming back to the phone, re-establishing the connection seems to fail.
I raised an issue with Fairphone’s bug tracker. Maybe someone else encounters similar issues? If so, please upvote the ticket. Link to the issue: https://bugtracker.fairphone.com/project/fairphone-android-7/issue/263