A battery-related problem with Garmin Fenix 6 smartwatches has been reported. Users claim that their batteries are draining at ~2% an hour, significantly reducing the wearable's lifetime. The issue was discovered following a recent firmware update. Garmin has since issued a new update though this does not resolve the problem; it is purely for diagnosis.
https://www.notebookcheck.net/Garmin-Fenix-6-models-develop-battery-health-issues-following-update.621149.0.html