Yup. It's really disappointing. But since it affects a lot of watches, apparently, I would say that it has to be a software issue. Since this issue exists basically since the devices' release, I would say that we might wait a long time until Samsung actually fixes it, if they ever will. I mean, since the release, they have released four or five system updates already (based on whether the first listed version is pre-installed on the initial release devices), the last having been released (at least here in Germany) Nov 18, and the problem still exists. I would be inclined to think that most people don't even notice it because they never even change any setting and just keep the default measurement every ten minutes while resting (which is borderline useless if you ask me, I also know the range of my heart rate when resting without having a wearable telling me...). These heart rate monitoring issues make it seem like it was not an accident, but actually intended (and not due to customer feedback or whatever) that they removed the continuous graph from the app and only show these useless min-max-bars, because they know exactly that there are issues with the continuous heart rate monitoring outside of a manually started workout.
Mine has another funny feature, after which I've decided to turn off the continuous measurement: Sometimes during the night, during which it usually measured accurately and without interruption, it would just completely give out and show only up to 5 values per hour, which were all above 140 and up to 194(!) bpm when the actual heart rate was quite a bit below 60bpm. I once woke up to seeing a reading of 172bpm. After I pressed the button to turn on the display, it immediately jumped to an appropriate value.
And for me, there's another pattern. Continuous mode without workout: Sets out once I move even the slightest bit, meaning it only shows the heart rate as if I was resting (which makes me think that they accidentally implemented some "detect while resting" feature like they did for the ten-minute measurement). Continuous mode with an automatically detected workout: Unrealistically flat line. Manually started workout: Perfect graph without interruptions and accurate values.
I had the store at which I've bought my previous Galaxy Watch 46mm (SM-R800, which was released ~3.5 years ago) send in the old one four times (the second time it got sent in, they ignored the visibly shifted backplate and just reset it; amazing...) because the heart rate monitoring sensor either had a shifted plate and had no heart rate reading due to that, or that the sensor just decided to show either no value or an unrealistically flat line. Now I've gotten this watch because, at least in terms of hardware, the sensor is much better, and it basically has the same issues, just that sending this watch in won't do anything because it's fairly obviously a software issue.
That's the thing with Samsung: Great hardware, garbage software during release. Every generation since the Gear S3 classic/frontier (if not even earlier devices) had some fitness-feature-related issue. The Galaxy Watch that I had also had issues with the heart rate monitoring even when the sensor seemed fine visually, it got less and less precise over time. Mine (Galaxy Watch SM-R800) never showed REM sleep, now the Watch4 Classic shows REM sleep but no deep sleep and also bad continuous heart rate monitoring. A relative's Gear S3 classic had a faulty workout recognition and some system bug early on that caused the battery to drain within less than twelve hours once an alarm was set. None of the watches counts the floors you've climbed... And honestly, I'm not buying other people's excuses anymore like "it's such a complex device with complex features", because no other manufacturer exhibits such issues.
I don't understand how it is possible to ruin such great hardware with such a bad software, and then repeat the same errors over and over again for years with every wearable fitness device. I'm really hoping for a comprehensive system update that fixes all of those issues soon.
