Audio Engine: Rare Unsupported Format Error

Question

I am experiencing a rare issue with AVAudioEngine, which I am using for speech recognition. While trying to start the audio engine, it immediately throws this error:

[ALERT ❌]::[14:26:25.2970]::The operation couldn’t be completed. (com.apple.coreaudio.avfaudio error -10868.)

An error code of -10868 translates to kAudioUnitErr_FormatNotSupported apart of the AudioToolbox library.

    private var mixerNode: AVAudioMixerNode = AVAudioMixerNode()
    audioEngine.attach(mixerNode)
    audioEngine.connect(audioEngine.inputNode, to: mixerNode, format: nil)
    
    let format = audioEngine.inputNode.outputFormat(forBus: 0)
    mixerNode.installTap(
        onBus: 0,
        bufferSize: 1024,
        format: format
    ) { (buffer, _) in
        self.recognitionRequest?.append(buffer)
    }
    
    do {
        audioEngine.prepare()
        try audioEngine.start()
    } catch {
        mixerNode.removeTap(onBus: 0)
        Log.error(error.localizedDescription)
    }