Subject: Optical Heart Rate Sensor Crash — HR Data Loss & Impact on Sleep/Body Battery
Device: Garmin Forerunner 970
Firmware Version: 6.18
Peripheral: Optical HR Sensor
Issue Summary:
During August 14-15, 2025, the optical heart rate monitor failed unexpectedly and stopped recording HR data. This triggered multiple false “Low HR Zone” alerts and prevented accurate physiological tracking. I did not realize the sensor had crashed until later, so I did not restart the watch immediately.
Impact:
- No heart rate data for the affected period.
- Sleep tracking failed entirely.
- Body Battery metrics were inaccurate due to missing HR and HRV inputs.
- Activity and recovery insights compromised.
Reproduction Steps:
- Normal wear during rest/sleep.
- Optical HR monitor stopped capturing data (no movement, no abnormal conditions).
- Device continued to show low or zero HR values.
- Only a restart would have resumed HR measurement (was not performed in time).
Expected Behavior:
- HR sensor should recover automatically from a temporary failure without requiring a restart.
- Fallback notification to the user when HR readings have been flatlined for more than a set threshold (e.g., 2–3 minutes) so corrective action can be taken immediately.
Suggested Fixes:
- Implement watchdog logic to reset optical HR module if readings are invalid for >X seconds.
- Add user alert for HR signal loss.
- Preserve sleep/Body Battery calculations using last valid HR/HRV until sensor resumes.
Attachments:
- [Optional: screenshots from Garmin Connect showing gap in HR data]