I'm having similar and very annoying issues with the (lack of) syncing of Fitness/Activity and Health between my Watch and my Phone.
These are (some of) the issues:
- When I use my Watch without the Phone nearby (at the gym), not all of my workouts are synced to the Fitness app on the phone. It seems my last Outdoor Walk never gets synced.
- The steps I take when using only the Watch get synced to the Phone Fitness app (even though one of the workouts doesn't register) - BUT the step count (and sometimes the Active Energy calorie count) doesn't sync to the Health app.
- A few times the Elliptical and Strength Training workouts are registered in the Fitness app (on Watch and Phone), but not in the Health app data
I had been working flawlessly for years, but when I recently tried the iOS 14 beta everything started to go bad.
I fixed it temporarily when I also installed the watchOS 7 beta, but the problems returned(?) when I installed the official iOS14/watchOS7 versions on the Phone and Watch. Strange.
I have tried rebooting, un-pairing/re-pairing and countless tweaks to the Data Sources and their priority.