Why does file download work on simulator but not on device?

Hi Apple developers,

I am new to IOS development and have recently added to my app the ability to download a file from a web API I created to be used in the app. The strange thing is this works fine in the simulator but when I plug in my IOS device I get these two errors:

nw_endpoint_handler_set_adaptive_read_handler [C2 192.168.1.67:5000 ready channel-flow (satisfied (Path is satisfied), viable, interface: en0, ipv4, dns)] unregister notification for read_timeout failed

and

nw_endpoint_handler_set_adaptive_write_handler [C2 192.168.1.67:5000 ready channel-flow (satisfied (Path is satisfied), viable, interface: en0, ipv4, dns)] unregister notification for write_timeout failed

Other endpoints from the web API that do not involve file downloads still work on the device.

The file type is a usdz model

Here is the code used to download and store the file:

class ModelFetcher: NSObject{
  var modelUrl: URL?
   
  func generateModel() {
    guard let url = URL(string: "http://192.168.1.67:5000/model.usdz") else {return}
    let urlSession = URLSession(configuration: .default, delegate: self, delegateQueue: OperationQueue())
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    let downloadTask = urlSession.downloadTask(with: request)
    downloadTask.resume()
  }
}

extension ModelFetcher: URLSessionDownloadDelegate {
  func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
    print("File Downloaded Location- ", location)
     
    let docsPath = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
    let destinationPath = docsPath.appendingPathComponent("model.usdz")
     
    try? FileManager.default.removeItem(at: destinationPath)
     
    do {
      try FileManager.default.copyItem(at: location, to: destinationPath)
      self.modelUrl = destinationPath
      print("File moved to: \(modelUrl!)")
    } catch let error {
      print("Copy Error: \(error.localizedDescription)")
    }
  }
}

Perhaps I have missed some configuration setting needed to allow file downloads on a device? Because, again, it works on the simulator but not on my own device, and, again, the other plain JSON endpoints still work on the device.

Any help would be much appreciated.

Thanks

Louis