HRM not recorded at night

Hi, I could use some swarm intelligence.
I've purchased a Bangle.js2 two weeks ago. During some nights no HRM or movement data were recorded. I already checked the designated app on the watch and could see a large gap beginning when I went to bed and ending when I got up in the morning. I already checked for the following:

1. wrist band tightly worn, a finger fits between band and skin but moving the finger is hard
   
2. watch not covered by pillow or other pressing material
   
3. even at nights where I read in bed but are still awake, no HR is recorded.
   
   

Before you might suspect that I didn't enable it, I have HRM's for the rest of the day.

Then, some other nights, I had records but they didn't show up in Gadgetbridge, all other HRM data earlier and later however are in the diagram. I should say, in the activity diagram because I don't have any data in the sleeping diagram.
Of these 2 weeks I own the watch only 3 nights show that I slept. The rest have no data at night.

Any thoughts on this?

I already checked the designated app on the watch

Is this maybe the health app or the sleeplog app?

I meant the health app.

Do you have any apps related to sleeping or night time installed? Or other apps related to heart rate?

If you do, one of those could maybe interfere with the recording of the health app recording hrm data during the night?

No, there was no related app installed.

Hi,

Sorry you're having trouble with this - so just to check, you're looking at the HRM graph in the Health app on the Bangle.js and seeing a gap, or you're looking in Gadgetbridge on your phone?

Is all your software up to date?

Also, Is HRM interval definitely set to something other than 'off' in health app settings?

Because the HRM can be turned on for other reasons during the day (eg the clock face requesting it) and the health app will save the data, but if HRM interval is off the health app won't actively turn the HRM on to get a reading.

Finally, is there anything you do on the watch at bedtime, like swapping apps or changing settings? Because it seems odd that the Bangle would stop recording the HRM so reliably...

Hi Gordon,
I had both cases:

1. No HRM during the night
   
2. When I had HRM during the night, I didn't have it in Gadgetbridge on my phone
   
   

HRM interval was set to 3 minutes. At bedtime, I did not change any settings.

What is your Bangle.js firmware version, and are the apps all up to date if you go to https://banglejs.com/apps/?

And are you sure you've removed the protective plastic off the bottom of the HRM sensor?

When I had HRM during the night, I didn't have it in Gadgetbridge on my phone

What do you mean here? That you saw you had HRM recorded over night in the Health app's graph, and yet it didn't appear on your phone in Gadgetbridge?

If anything the heart rate monitor tends to guess the heart rate, so about the only way it'd stop recording heart rate is if the proximity sensor on the back didn't think the watch was being worn at all.

Please could you connect with the Web IDE and then paste this code into the left-hand side:

Bangle.setHRMPower(1);Bangle.on("HRM-raw",h=>g.clear(1).setFont("6x8").drawString(JSON.stringify(h,null,2)));

Specifically I'm interested in the vcPS value that's displayed on the screen when you're wearing normally and when you're pressing the watch onto and on the side of your arm as if you might be lying down.

Normally for me, vcPS is at 15 pretty much all the time when I'm wearing the watch, but if for some reason yours is dropping to below 7 the watch could be thinking it's not being worn and so not recording a value