current use of background-tasks leads to crashes

[bluegaspode]

You currently use background tasks without expiration handlers.
If a background task expires while the App is in the background, it will be killed by iOS (from my observations it seems like this happens only after 24hours - or when the App is restarted later on)

From the documentation of the expirationHandler:

"A handler to be called shortly before the application’s remaining background time reaches 0. You should use this handler to clean up and mark the end of the background task. Failure to end the task explicitly will result in the termination of the application. The handler is called synchronously on the main thread, thus blocking the application’s suspension momentarily while the application is notified."

Futhermore it should be enough to start exactly one background task when the Queue is stopped. While playing the App will not be suspended (if the App declares 'audio' as it's background mode).