I get the same crash and stacktrace calling the following but only on 15.1.x. 15.0 and 15..2x and above do not crash. Hopefully this was an iOS bug that got fixed. AVAudioSession.sharedInstance().requestRecordPermission({(granted: Bool)-> Void in

Thank you. We were asked because our HW devices have code to limit it to IGMP v2. Our customer's network has an issue due to a bug on their CISCO router for which there is no fix yet.