Update: resigning and restoring first responder did not resolve the issue (thought it does look much nicer with the privacy screen). Really desperate for a fix here.

Update: SOLVED IT! We were accidentally doing navigation in the background, which was still happening when we called the completionHandler, which triggered a new snapshot, which crashes when navigation is in progress. Solution: inside application(_:, didReceiveRemoteNotification:, fetchCompletionHandler:), before doing any navigation, guard that case .inactive = application.applicationState, otherwise return. That worked for us!