I have a watch4 classic with the latest updates and notices my stress measurement wasn't working. So, after hours of trying to figure this out, and multiple resets I finally figured out why the stress measurement is not working for some users. On my watch, if I install YouTube music, the stress measurement immediately stops working. If I try to manually measure it gets to 51% then jumps to 100 and fails. The measurement is always at zero. If I uninstall YouTube music it works immediately. If you are experiencing this issue try uninstalling YouTube music. This is a bug either google or Samsung will need to figure out.
My GW4 has been doing the same thing almost since I got it. Gets to 60 -65 percent and then rolls to 100 and shows stress as none. I just removed the only music program iheart and it did not fix. I did not reboot watch and phone so that might be it or some other program. I am sure that is the problem because it worked correctly out of the box. The odd thing is it worked once last week when I tried it and I thought it was fixed but never worked again. The only other problem I have had and not been able to solve is the speaker volume gave up about six months in so I cannot hear people when they call but I can answer and switch call to phone just cannot hear them or youtube or music but bluetooth ear pods work so i know it is watch speaker hardware not software. I am considering trading for the GW5 to fix these issues and get larger battery if I can get a good enough deal.