From Actualidad iPhone we never advise be one of the first to update your device to new versions of iOS or updates that it releases periodically at least until we know (through user opinions) that we are not going to find any problems.
The first problem faced by the first users who update their iPhone to iOS 14 and their Apple Watch to watchOS 7 affects the operation of the GPS, GPS that does not correctly record training routes. It does not matter if we use the Apple application or one of third parties.
When many users were waiting for an update to be released from Cupertino to solve this problem, Apple's support page invites us to restore both devices from scratch to solve the problem.
If Apple recommends that this is the only or recommended solution to fix this problem, this is because the problem is in the update process of both devices, a process that will cause certain files to not work correctly, so the only solution es make a clean slate.
This problem has occurred mainly in the users who have upgraded from iOS 13 to iOS 14. Users who reset both the Apple Watch and the iPhone have not experienced these GPS performance issues.
Every time Apple releases a new version of any of its operating systems, the best we can do is restore from scratch without loading a previous backup, since we would drag the possible performance or operation problems that the device was presenting.
After restoring my iPhone 8 Plus and my Apple Watch series 4 I can tell you that it continues to present exactly the same problems ...
iPhoneX with IOS 14.0.1 and Apple Watch series 2 with WatchOS 6.2.8 (17U63).
After restoring both, the GPS problem continues. I still can't see the route of my training.