Got version 14.15 fresh today.
Then soft reset, and new pairing in the GC app.
During a 20min walk, the activity jumped back to the Watchface several times with the error message "media error" ("Medienfehler" in German..). In the background, the activity continues, but no GPS is recorded.
Hereafter soft reset again.
Again started a walking activity, after 2min the same error, resumed to activity-screen, 5 minutes later the same...
EDIT: No Media was played, there wasn´t even a connection to headphones.
EDIT2: Tryed with Cardio-activity: Error after 3 Minutes......
EDIT3: Tried out different things, what have worked is switched my Watchface to a Regular one. Since than no Problems. Switching back to custom "Quatro"-Watchface, problems appeared again.