Depth Data Collected not Working

I am collecting depth data to generate depth maps for my app. The depth data worked properly at first. However, after a few rounds of testing (while the code has not been changed), the program seems to be unable to collect proper depth data as when I print the depth data, it says

<AVDepthData: 0x2801dc610 0x0 (low/rel) (unfiltered)>

, which is clearly not a valid AVDepthData to use.

Following is the chunk of code:

func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {
     
    if error != nil {
      return
    }
     
    guard let imageData = photo.fileDataRepresentation() else {return}
     
    self.picData = imageData

    let depthData = photo.depthData!

    DispatchQueue.main.async {
       
      let depthPixelBuffer = depthData.depthDataMap
         
        if !self.photoDepthConverter.isPrepared {

          var depthFormatDescription: CMFormatDescription?
          CMVideoFormatDescriptionCreateForImageBuffer(allocator: kCFAllocatorDefault, imageBuffer: depthPixelBuffer, formatDescriptionOut: &depthFormatDescription)

          if let unwrappedDepthFormatDescription = depthFormatDescription {
            self.photoDepthConverter.prepare(with: unwrappedDepthFormatDescription, outputRetainedBufferCountHint: 3)
          }
        }
                  
        guard let convertedDepthPixelBuffer = self.photoDepthConverter.render(pixelBuffer: depthPixelBuffer) else {
          print("Unable to convert depth pixel buffer")
          return
          }
         
        let greyImage = UIImage.init(pixelBuffer: convertedDepthPixelBuffer)
         
        self.depthImage = greyImage!
      
    }
  }
     

Note: it is not a problem that always occurs. When I change the ios deployed version, initially, the problem seems to be solved, but when I cleaned and built again, the problem reoccurs.

I also tried to mode the declaration for depthData to be above imageData. Again, initially the problem seems to be solved, but after a feel testing trials, the problem reoccurs.