When I bought new bikes for myself and my wife I decided to buy for both a speed sensor v2. The idea was that I would have all rides registered on the speed sensor itself or on our fenix watches. In theory perfect, but it just won't work.
In reality I save all rides using my fenix 7x and I removed the sensor for my wife's fenix 6s to make sure it does record and syncs them to her phone. I just won't work with the sensor connected to the phone as well as the watch.
Connecting the sensor to both does work as long as there is no interaction with the watch, a notification or a message or something can be enough for the sensor not to save/sync the ride to garmin connect.
I would suggest a solution for that issue and next to posting here to give the option for comments I will also post it on the garmin ideas page: Submit idea If you like the idea, please also post there so there is more chance the developers will look into this option.
Solution:
Let the sensor save all rides and sync those to garmin connect via the phone (or optionally even maybe through the connected device like edge/fenix/forerunner/etc).
When I record a bike ride on another device, like edge/fenix/etc those also get synced to garmin connect, but when the backend detects that there is a speed sensor connected it checks for the activity saved by that sensor and merges those activities.
That would lead to multiple activities inside garmin connect: the sensor, the watch/edge one and a merged one. There can be even multiple ones from the sensor or watch/bike computer inside that merged one.
To avoid having multiple rides directly visible all activities except for the merged one should be hidden, but accessible using the merged one. A simple list of links inside that one activity is enough. The logic can also make sure all distance is only counted once.
For automatic upload to services like strave: give the option to only upload the saved one(s) on the watch/bike computer or the complete merged one.
Advantages:
All rides are synced anyway, so no more lost activities (rides) as most important one.
For users that would like to save a bike ride but keep the first/last part hidden can have an activity with the complete ride for themselves, but hide certain parts for sharing rides by saving the part they want to share as a seperate activity.
Option to save a warmup, race and cooldown in different activities, but have the sensor active between steps which creates a complete overview for training analysis purposes without the need to manually extract the phases if you want those statistics.
