title: UNNotificationServiceExtension sometimes doesn't run
body: <p>I'm working on an application which uses an UNNotificationServiceExtension. Most of the time (something like 90%) my extension runs correctly, makes a connection the the backend and then displays the notification. But seems like sometimes the extension doesn't run at all and the system displays the original message inside the notification. Why does this happen? All notifications definitely contain the mutable-content key set to 1.</p>