Batch transcribe from file fails on all but the last, async problem?

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I am attempting to do batch Transcription of audio files exported from Voice Memos, and I am running into an interesting issue. If I only transcribe a single file it works every time, but if I try to batch it, only the last one works, and the others fail with No speech detected. I assumed it must be something about concurrency, so I implemented what I think should remove any chance of transcriptions running in parallel. And with a mocked up unit of work, everything looked good. So I added the transcription back in, and

1: It still fails on all but the last file. This happens if I am processing 10 files or just 2.

2: It no longer processes in order, any file can be the last one that succeeds. And it seems to not be related to file size. I have had paragraph sized notes finish last, but also a single short sentence that finishes last.

I left the mocked processFiles() for reference.

Any insights would be greatly appreciated.

import Speech
import SwiftUI

struct ContentView: View {
    @State private var processing: Bool = false
    @State private var fileNumber: String?
    @State private var fileName: String?
    @State private var files: [URL] = []
    
    let locale = Locale(identifier: "en-US")
    let recognizer: SFSpeechRecognizer?
    
    init() {
        self.recognizer = SFSpeechRecognizer(locale: self.locale)
    }
    
    var body: some View {
        VStack {
            if files.count > 0 {
                ZStack {
                    ProgressView()
                    Text(fileNumber ?? "-")
                        .bold()
                }
                Text(fileName ?? "-")
            } else {
                Image(systemName: "folder.badge.minus")
                Text("No audio files found")
            }
        }
        .onAppear {
            files = getFiles()
            Task {
                await processFiles()
            }
        }
    }

    private func getFiles() -> [URL] {
        do {
            let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
            let path = documentsURL.appendingPathComponent("Voice Memos").absoluteURL
            
            let contents = try FileManager.default.contentsOfDirectory(at: path, includingPropertiesForKeys: nil, options: [])
            
            let files = (contents.filter {$0.pathExtension == "m4a"}).sorted { url1, url2 in
                url1.path < url2.path
            }
            
            return files
        }
        catch {
            print(error.localizedDescription)
            return []
        }
    }
    
    private func processFiles() async {
        var fileCount = files.count
        for file in files {
            fileNumber = String(fileCount)
            fileName = file.lastPathComponent
            await processFile(file)
            fileCount -= 1
        }
    }
    
//    private func processFile(_ url: URL) async {
//        let seconds = Double.random(in: 2.0...10.0)
//        await withCheckedContinuation { continuation in
//            DispatchQueue.main.asyncAfter(deadline: .now() + seconds) {
//                continuation.resume()
//                print("\(url.lastPathComponent) \(seconds)")
//            }
//        }
//    }
    private func processFile(_ url: URL) async {
        let recognitionRequest = SFSpeechURLRecognitionRequest(url: url)
        recognitionRequest.requiresOnDeviceRecognition = false
        recognitionRequest.shouldReportPartialResults = false
        
        await withCheckedContinuation { continuation in
            recognizer?.recognitionTask(with: recognitionRequest) { (transcriptionResult, error) in
                guard transcriptionResult != nil else {
                    print("\(url.lastPathComponent.uppercased())")
                    print(error?.localizedDescription ?? "")
                    return
                }
                if ((transcriptionResult?.isFinal) == true) {
                    if let finalText: String = transcriptionResult?.bestTranscription.formattedString {
                        print("\(url.lastPathComponent.uppercased())")
                        print(finalText)
                    }
                }
            }
            continuation.resume()
        }
    }
}

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