This week's Watch OS 1.0.1 update has caused some Apple Watches to track heart rate sporadically, in some cases with an hour or more between readings, according to complaints on Apple's support forums, and verified by AppleInsider's own tests.
Watch owners first began complaining about the issue on Wednesday, noting that Apple officially states that the Watch should take a reading every 10 minutes outside of the Workout app. In some cases the Watch is not only taking much longer to obtain a reading, but failing to do so at all unless wearers launch Workout or an appropriate Glance.
Workout tracking appears to functional normally for the most part, although one poster on Apple's forums said that during a bike ride his Watch was stuck searching for a heart rate, something he'd never seen prior.
One AppleInsider editor observed on Friday that until he forced a reading, his Watch hadn't recorded any heart rate data since Thursday, despite having worn the device for hours.
Apple has so far experienced a mixed public reaction to the Watch's heart rate sensor. While the technology has made the Watch a pick for a handful of medical trials, the company was also forced to admit that it may not work at all with wrist tattoos.
When it is working, however, the accuracy of the Apple Watch's heart rate sensor has been praised for its accuracy, especially when considering many wrist-worn heart rate monitors have historically been unreliable. One test conducted earlier this month found that the Apple Watch's heart rate sensor is essentially on par with the Mio Alpha, a dedicated heart rate tracker also worn on the wrist.