PSA: Look at the heart rate sensor of your fenix 5. Has it cracks like mine? If yes, it's a common problem. Send it to Garmin and get a free replacement. Do
Garmin Fenix 5/5S/5X Plus In-Depth Review (with Maps, Music, Payments) | DC Rainmaker
Garmin Fenix 5 Review: The Best Outdoor GPS Watch | Tom's Guide
fēnix® 5S Plus
Fenix 5 & 5s RECALL ? - Would you do that if you were Garmin right now?