I'm one of those affected by the bug, and in my case no amount of restoring has helped at all. Worse yet, while I'm not seeing a decrease in battery life on my AW4, it's pretty bad on my iPhone 11.
One thing I noticed is that the watch is missing from the list of workout route data sources in Health.app (in my case I have a few "older" watches from previous restores, but not the "current" ones after watchOS 7 / iOS 14). In my humblest opinion — not an Apple engineer but a general tinkerer and developer — that's a big part of the problem: routes are not saved because the watch is not even registered as a potential data source for them.
That shouldn't affect older routes as they're theoretically already saved in Health and all Fitness has to do is read them, but I wouldn't be surprised if the upgrade to iOS 14 just accidentally wiped those out due to some glitch, leaving botched metadata behind. Moreover, I discovered almost by accident that GPS data was not being recorded for my walks since the 1st of September, which coincides with the release of iOS 13.7. Whether that has had a part in my specific disaster is anyone's guess.
I still get a high CPU usage by Health.app despite the restore from backup of both iPhone 11 and Watch 4 (my health database is probably seriously broken, unlike others who got things back), resulting in the device becoming burning hot and the OS killing "healthd"; the d indicating that it's a daemon (background service). With that failed and not restarted until later on, it would explain why sometimes we get gaps in the stand hours or exercise minutes, though the tallies get updated. The watch just pushes that individual hours data once to the phone, always expecting that it succeeds, and never tries again because it just doesn't know it failed. The tallies are updated multiple times, so even if it misses going from 5 to 6 the first time, it will likely manage to do it when it updates the calories or something else anyway.
At least, that's my take on it. Fingers crossed Apple sorts this out soon, because it's really frustrating. I personally don't care much about my routes, though having botched data does irk me. Even worse, I never know if opening any health-related app may trigger that bug and burn up 6-7% of battery life. It just feels like the whole ecosystem suddenly became extremely flaky and unreliable, which is a huge bummer.
If anyone is affected by the bug and wants to see if the Health background service also gets killed on their phone, just go to Settings - Privacy - Analytics - Analytics Data, and search for "healthd.cpu_resource-..."). If it's there, it will probably say something like this:
Event: cpu usage
Action taken: none
CPU: 90 seconds cpu time over 139 seconds (65% cpu average), exceeding limit of 50% cpu over 180 seconds
CPU limit: 90s
Limit duration: 180s
CPU used: 90s
CPU duration: 139s
Duration: 139.01s
Duration Sampled: 137.67s
Steps: 174
Fingers crossed we don't have to wait for 14.2 for this to get solved, as that's likely coming well after the new iPhones.
