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Fenix 8 -Big problems

MaciejHassak
5 months ago

Hello,

I have a serious issue with my Fenix 8. Specifically, I rode on Zwift for one hour and burned exactly 665 kcal. Shortly after, all the data synced to Garmin Connect, and on the watch, it shows nearly 1200 kcal burned, as you can see in the photo.

To clarify, it’s still morning, and before starting the workout, my burned calories were at 0. In the second photo, you can see two spikes on the graph, where in one minute, I supposedly burned nearly 600 kcal.

This is the fourth time I’ve noticed this. Yesterday morning, I also had a similar calorie spike in one minute while just sitting on the bed. This has become quite concerning, so I decided to make this post.

Another issue I’ve noticed is that the heart rate sensor is not working properly. For example, when walking up the stairs quickly, the watch might show a maximum of 120 bpm unless I check the heart rate directly on the watch. When I swipe to the heart rate panel, it then adjusts and shows 140 bpm immediately. It’s as if I need to open the heart rate display for it to work correctly; otherwise, it underestimates the value.

I’m attaching two photos to illustrate the issue. Could someone please help? Is this a hardware issue, or could it be a software problem?

  • 0 5 months ago

    Hi, your second issue seems to be normal to me. 
    In non activity mode your watch does not track your heart rate that often to safe battery life.
    Once you are in an activity, on the heart rate data sheet or enable heart rate broadcasting, the reading rate goes up and it should be more precise. 

  • 0 5 months ago in reply to MobyDuck

    Was your kcal calculation of 665 based in Zwift or the indoor cycling activity on your watch?

    Also, I’ve had my watch (not Fenix 8) pick up a second activity as MoveIQ which I’ve since disabled. 

  • 0 5 months ago in reply to MobyDuck

    To be precise, watch does measure heart rate every single second all the time, but there is low power mode while just wearing them. You can see it on the led diodes. While not in activity, just two of them are active and not too bright. While activity or watching the HR glance, broadcasting HR, etc., all green diodes are active and very bright.

  • 0 5 months ago

    Hello,
    Continuing the saga of issues. Please check this yourselves if any of you ride on Zwift – this is quite a curious bug.

    I thought that yesterday’s calorie spike might have been caused by the fact that the watch was lying motionless on the table but close to my trainer and me, where all the data was being transmitted while I was doing my workout.

    Today, I took the watch to another room and closed the door to keep it as far away as possible. I emphasize that the watch lay completely still during the 45-minute workout.

    When I finished riding, I ended the session on Zwift, which automatically uploaded to Garmin Connect. I went to check the calories again to see if anything had been miscalculated. To my surprise, I took a photo and captured something strange – the watch had registered over 600 steps while lying completely still!

    This is, in my opinion, another serious bug. I hope someone from Garmin is reading this because this isn’t the first time I’ve encountered it. Otherwise, let me know where I can report this. I noticed this issue once before, but I dismissed it as my mistake. However, today I have undeniable proof.


    You didn’t fully understand my issue in your previous replies. The problem is that when the watch is in battery-saving mode, it seems to miscalculate heart rate and, consequently, calories.

    Here’s what I mean: if I’m walking fast and my actual heart rate is 120 bpm, but I don’t wake up the watch to check, it might measure, for example, 100 bpm instead. It seems like only when I interact with the watch (e.g., by swiping to view the heart rate widget), it suddenly "wakes up," adjusts quickly, and then shows the correct 120 bpm.

    The concern is that when I’m running and my heart rate is actually 120 bpm, the watch might be recording a lower heart rate instead of the real value. I’ve noticed this a few times – for example, when running up stairs, I feel my heart rate is high, but when I check the watch, it shows something like 106 bpm. After a few seconds, it suddenly updates to 120 bpm.

    My question is: if I don’t interact with the watch to wake it up, does it actually record the correct 120 bpm in the background, or is it storing inaccurate lower values?

    That’s my concern.

  • Former Member
    0 Former Member 5 months ago in reply to MaciejHassak
    MaciejHassak said:
    To my surprise, I took a photo and captured something strange – the watch had registered over 600 steps while lying completely still!

    I have heard of this happening, and it turned out to be a fan or something that caused vibration enough to make the device count steps while just sitting on a table or night stand.

  • 0 5 months ago in reply to MobyDuck

    Fenix 8 and other Garmin watches are measuring heart rate 24/7 unlike smartwatches from Apple/Samsung or Google

  • 0 5 months ago in reply to Former Member 
    Please read carefully - I deliberately took the next room and locked the room.
  • 0 5 months ago in reply to MaciejHassak
    MaciejHassak said:
    the watch had registered over 600 steps while lying completely still!

    Do you happen to use the HRM-Pro or HRM-Fit strap when riding the indoor bike on Zwift? If so, then the steps come from it. 

  • Former Member
    0 Former Member 5 months ago in reply to MaciejHassak

    What I'm saying is, if you put it in a room where there is any type of vibration (even slight) can be felt by the device, it can possibly count steps. Vibration can travel through solid objects to other solid objects.

  • 0 5 months ago in reply to Former Member

    That's an interesting thought. I guess no electric tooth brushing with the non-dominant hand.