Deactivate AudioSession in AudioKit - swift

Question

I'm using AudioKit, and trying to set audio session inactive, when I don't need it. So, I wrote some simple code to understand mechanism of this process, and faced one unexpectable trouble. With attempts of deactivating session, I'm getting error:
[avas] AVAudioSession.mm:1079:-[AVAudioSession setActive:withOptions:error:]: Deactivating an audio session that has running I/O. All I/O should be stopped or paused prior to deactivating the audio session.
ViewController.swift:deactivateAudioSession():73:Error Domain=NSOSStatusErrorDomain Code=560030580 "(null)"
This is my sample code:
import UIKit
import AudioKit
class ViewController: UIViewController {
var reverb: AKReverb?
var delay: AKDelay?
var chorus: AKChorus?
var mic: AKMicrophone!
override func viewDidLoad() {
NotificationCenter.default.addObserver(self, selector: #selector(applicationWillResignActive),
name: UIApplication.willResignActiveNotification,
object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(applicationDidBecomeActive),
name: UIApplication.didBecomeActiveNotification,
object: nil)
super.viewDidLoad()
AKSettings.useBluetooth = true
guard let mic = AKMicrophone() else { return }
self.mic = mic
chorus = AKChorus(mic)
chorus?.depth = 1
chorus?.frequency = 44000
let delay = AKDelay(chorus)
delay.feedback = 0.2
reverb = AKReverb(delay)
let mix = AKMixer(reverb)
AudioKit.output = mix
}
#IBAction func launchEngine() {
do {
try AudioKit.start()
} catch {
AKLog(error)
}
}
#IBAction func deactivateAudioSession() {
// mic.stop()
// reverb?.stop()
// delay?.stop()
// chorus?.stop()
do {
try AKSettings.session.setActive(false)
} catch {
AKLog(error)
}
}
#objc func applicationDidBecomeActive() {
launchEngine()
}
#objc func applicationWillResignActive() {
deactivateAudioSession()
}
}
As you can see, basically, I wanted to handle app state changing, but this error happens even if I call deactivateAudioSession() method using UI. I've tried to stop() all node objects (commented code) before deactivation, but error stays. What I'm doing wrong?