Issue rendering offline to AVAudioPCMBuffer

Question

I am trying to use Audiokit’s AudioEngine.Render() function to synthesize some audio and write it to an AVAudioPCMBuffer. I believe I am using the render function incorrectly. I haven’t been able to find any examples of this. Below is my code. What is the proper usage for this? I am assuming my process is incorrect as I am setting this up similar to a realtime renderer solution.

import AudioKit
import SoundpipeAudioKit
import AVFAudio

class RenderIssue
{
    var engine = AudioEngine()
    var whtns = WhiteNoise()
    var filter: BandPassFilter
    
    init(){
        whtns.amplitude = 1
        filter = BandPassFilter(whtns)
        filter.bandwidth = 200
        filter.centerFrequency = 1000
        
        engine.output = filter

        do{
            try engine.start()
        }
        catch let err
        {
            print(err)
        }
        
        whtns.start()
        filter.start()
    }
    
    // Called from button click
    func startRender()
    {
        // buffer creation
        var buffer = AVAudioPCMBuffer(
            pcmFormat: engine.avEngine.outputNode.outputFormat(forBus: 0),
            frameCapacity: 48000
        )

        // Try 1
        buffer = engine.render(duration: 1)
        
        // Try 2
        do
        {
            try engine.avEngine.renderOffline(1, to: buffer!)
        }
        catch let err
        {
            print("Render Error" + String(describing: err))
        }
    }
}

On both attempts I get the following issue

AVAEInternal.h:76    required condition is false: [AVAudioBuffer.mm:286:-[AVAudioPCMBuffer initWithPCMFormat:frameCapacity:]: (isPCMFormat(fmt))]

2022-02-03 11:42:08.248120-0800 SynthClap[54704:1387670] *** Terminating app due to uncaught exception 'com.apple.coreaudio.avfaudio', reason: 'required condition is false: isPCMFormat(fmt)'