I've actually seen this problem for a while (several months), but hadn't bothered to mention it here until now:
Maybe once or twice per week Bluetooth seems to stop working properly; my fitness tracker doesn't sync anymore. I see brief communication attempt in the app / app's sync icon in notifications but no new data appears in the app. If I eg. try to scan for BT devices in this state, no devices seem to be found even if I know there are several nearby.
A quick workaround is just to toggle to flight mode and back (probably toggling just BT would work too) so it's more of a minor annoyance than a big problem, but I'd still be interested if others are seeing this too.