AVAssetWriterInput.append giving error "An Unknown Error Occurred (-12706)"

I am simply trying to capture the screen, app audio and mic audio. The app audio and mic audio independently work fine but when combined some unknown error is thrown. Following are the methods to start the capture of screen and processSampleBuffer.

Method to setup writers for screen capture

func startCapture() {
        _filename = UUID().uuidString
        let videoPath = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!.appendingPathComponent("\(_filename).mp4")
        let writer = try! AVAssetWriter(outputURL: videoPath, fileType: .mp4)
        
        let screen = UIScreen.main.bounds
        let screenBounds = screen.size
        let videoCompressionPropertys = [
            AVVideoAverageBitRateKey: screenBounds.width * screenBounds.height * 10.1
        ]
        
        let videoSettings: [String: Any] = [
            AVVideoCodecKey: AVVideoCodecType.h264,
            AVVideoWidthKey: screenBounds.width,
            AVVideoHeightKey: screenBounds.height,
            AVVideoCompressionPropertiesKey: videoCompressionPropertys
        ]
        
        let input = AVAssetWriterInput(mediaType: .video, outputSettings: videoSettings)
        input.expectsMediaDataInRealTime = true
        if writer.canAdd(input) {
            writer.add(input)
        }
        
        // Add the app audio input
        var acl = AudioChannelLayout()
        memset(&acl, 0, MemoryLayout<AudioChannelLayout>.size)
        acl.mChannelLayoutTag = kAudioChannelLayoutTag_Mono;
        let audioOutputSettings: [String: Any] =
        [ AVFormatIDKey: kAudioFormatMPEG4AAC,
       AVSampleRateKey : 44100,
 AVNumberOfChannelsKey : 1,
   AVEncoderBitRateKey : 128000,
    AVChannelLayoutKey : Data(bytes: &acl, count: MemoryLayout<AudioChannelLayout>.size)]
        
        let audioInput = AVAssetWriterInput(mediaType: AVMediaType.audio, outputSettings: audioOutputSettings)
        audioInput.expectsMediaDataInRealTime = true
        if (writer.canAdd(audioInput)) {
            writer.add(audioInput)
        }
        
        
        // Add the mic audio input
        let audioOutputSettings1: [String: Any] =
        [ AVFormatIDKey: kAudioFormatMPEG4AAC,
       AVSampleRateKey : 24000,
 AVNumberOfChannelsKey : 1,
AVEncoderAudioQualityKey: AVAudioQuality.high.rawValue]
        
        let micAudioInput = AVAssetWriterInput(mediaType: AVMediaType.audio, outputSettings: audioOutputSettings1)
        micAudioInput.expectsMediaDataInRealTime = true
        if (writer.canAdd(micAudioInput)) {
            writer.add(micAudioInput)
        }
        
        writer.startWriting()
        
        _audioAssetWriterInput = audioInput
        _micAssetWriterInput = micAudioInput
        _assetWriterInput = input
        _assetWriter = writer
    }

processSampleBuffer

override func processSampleBuffer(_ sampleBuffer: CMSampleBuffer, with sampleBufferType: RPSampleBufferType) {
        if startTime == nil {
            startTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
            
            _assetWriter!.startSession(atSourceTime: CMTime.zero)
        }
        
        if sampleBufferType == RPSampleBufferType.video {
            if let _assetWriterInput = _assetWriterInput {
                if _assetWriterInput.isReadyForMoreMediaData {
                    let appended = _assetWriterInput.append(sampleBuffer)
                    print(appended)
                    
                    if !appended {
                        let status = _assetWriter?.status
                        let error = _assetWriter?.error
                        print("cannot append video")
                    }
                }
            }
        }
        
        if sampleBufferType == RPSampleBufferType.audioApp {
            if let _assetWriterInput = _audioAssetWriterInput {
                if _assetWriterInput.isReadyForMoreMediaData {
                    let appended = _assetWriterInput.append(sampleBuffer)
                    print(appended)
                    
                    if !appended {
                        let status = _assetWriter?.status
                        let error = _assetWriter?.error
                        print("cannot append app audio")
                    }
                }
            }
        }
        
        if sampleBufferType == RPSampleBufferType.audioMic {
            if let _assetWriterInput = _micAssetWriterInput {
                if _assetWriterInput.isReadyForMoreMediaData {
                    let appended = _assetWriterInput.append(sampleBuffer)
                    print(appended)
                    
                    if !appended {
                        let status = _assetWriter?.status
                        let error = _assetWriter?.error
                        print("cannot append mic audio")
                    }
                }
            }
        }
        
        if shouldEnd {
            _finishWriters()
        }
    }