Hello, I have the same problem with vivosmart 4. The activity can be accessed here : connect.garmin.com/.../5014343772
The activity can be accessed here
Unfortunately it cannot. You have to change the privacy level of that respective activity to "Everyone" (click on the lock symbol up right on the activity screen)
Yes, it looks like a bug, probably caused by the fact that the GPS data comes from an external device, not from the Vivosmart self. Report it to Garmin Support, perhaps they are not aware of it.