Meg -
You may well be right, though I highly doubt it. 35+ years working in high tech, including working with, designing, and manufacturing embedded devices, tells me that it's a software bug. I've also spent that 35+ years working in the field (software engineering ...) where "reboot your gadget" or "reinstall your software" are common solutions to software problems that never get fully investigated or resolved.
There are many dozens of threads in this forum all related to errors in the various fitness apps. If they are all caused by hardware problems (very doubtful - Apple makes very high quality hardware and I have Apple products in half a dozen rooms in my house, plus on my wrist and in my purse, and this would be my very first Apple hardware problem ...), Apple has a serious hardware quality assurance or design issue. It is far more likely that this is a software bug, just like people who work at standing desks who don't get "Stand" hour credits.
Please, if I am causing you personal angst, just don't hit the "Reply" button. No one is making you do that.