Given the fact that it's a software issue along with a whole array of issues regarding the sensors (like the watch stopping continuous heart rate measurement when resting, or the measurements being unreliable outside of the workout mode like is the case with me) that appeared after the update that added "An improved HR measurement accuracy algorithm" has been released, the only way to get this issue fixed is another system update. Mine doesn't record deep sleep properly as well. And this deep sleep recording issue doesn't just affect the Galaxy Watch4, but also the Galaxy Watch since the update to Tizen 5.5.0.2 that added this new algorithm. I've experienced the issues with both watches (although I can't confirm whether any issues were there prior to the update on the Watch4 because I bought mine in early December and it has been produced after the latest update to the version DUK1 has been released, meaning it has already been pre-installed on my watch), and there doesn't appear to be any fix regarding any sensor issues or the measurement algorithms. Resetting the watch to factory defaults or any other things that you might do with the software won't fix these issues.
So I guess we're left with waiting for an OS update. The most current one I could find for the Watch4 at least is the version R890XXU1DULB that appears to have only been released in South Korea as of yet, but with the rather standard, unspectactular, non-saying description "Improved system stability and reliability". Let's hope that it fixes such issues, should this even get released anywhere outside of South Korea.
