I don’t think it is a software or hardware issue. My HR monitor, steps counter and others working fine accurately before and after the software update.
In addition, after the software update (as it mentions better battery management), I can get a forecast of 2 days some hours based on my usage pattern. I used to get 1 day and 23hrs max on a full charge.
Also, the GW was released in other countries since Aug 2018. There has not been any reviews, news of such software or hardware bug, issue going on.
Am using a 42mm Black and happy till now.
Cheers!