PSA: Don't update to iOS 12.4 if you use apps in AB output slot or IAA apps that use the mic.
https://forum.audiob.us/discussion/34030/urgent-psa-hold-off-updating-to-ios-12-4-if-you-use-apps-in-output-slot-in-audiobus
https://forum.audiob.us/discussion/34030/urgent-psa-hold-off-updating-to-ios-12-4-if-you-use-apps-in-output-slot-in-audiobus
General App Discussion
Discussions about apps in general