When you're tracking an activity and receive a system notification such as a Health/Activity ring notification, phone call, does the app crash? You're not alone. This is a pesky bug and if you write to firstname.lastname@example.org with "Apple Watch: Notification Bug" in the subject line, we'll be sure to keep you updated when we have any news. In the meantime, some users have elected to disable these notifications on their Watch. If you like, you can do so by opening the Watch app on your phone, then tapping Notifications->Activity, and disabling the Goal Completions toggle.