Downsampling images in Isaac SDK

I’m using a MIPI/CSI Camera on Jetson Xavier NX.
Since it doesn’t support lower resolutions than 720p, I want to downsample the image coming from the isaac::ArgusCsiCamera node.
When I try to downsample the image using CropAndDownsample component in the argus_camera sample, a black image appears in websight image viewer.

This is my modified argus_camera.app.json file:

  {
  "name": "argus_camera",
  "modules": [
    "perception",
    "sensors:argus_camera",
    "sight",
    "viewers",
    "cask"
  ],
  "config": {
    "websight": {
      "WebsightServer": {
        "port": 3000,
        "ui_config": {
          "windows": {
            "Argus Image": {
              "renderer": "2d",
              "dims": {
                "width": 1280,
                "height": 720
              },
	      "custom_dimensions": true,
              "channels": [
                {
                  "name": "argus_camera/color_camera_viewer/viewer/image"
                }
              ]
            }
          }
        }
      }
    },
    "argus": {
      "camera": {
        "mode": 4,
        "camera_id": 0,
        "framerate": 60,
        "focal_length": [
          700.0,
          700.0
        ],
        "optical_center": [
          360.0,
          640.0
        ]
      }
    },
    "image_cropper": {
      "cropper": {
	"downsample_size": [640, 360]
      }
    },
    "color_camera_viewer": {
      "viewer": {
      	"target_fps": 100
      }
    }
  },
  "graph": {
    "nodes": [
      {
        "name": "argus", 
        "components": [
          {
            "name": "isaac.alice.MessageLedger",
            "type": "isaac::alice::MessageLedger"
          },
          {
            "name": "camera",
            "type": "isaac::ArgusCsiCamera"
          }
        ]
      },
      {
        "name": "color_camera_viewer",
        "components": [
          {
            "name": "isaac.alice.MessageLedger",
            "type": "isaac::alice::MessageLedger"
          },
          {
            "name": "viewer",
            "type": "isaac::viewers::ImageViewer"
          }
        ]
      },
      {
      	"name": "image_cropper",
	"components": [
          {
            "name": "isaac.alice.MessageLedger",
            "type": "isaac::alice::MessageLedger"
          },
	  {
	    "name": "cropper",
	    "type": "isaac::perception::CropAndDownsampleCuda"
	  }
	]
      }
    ],
    "edges": [
      {
        "source": "argus/camera/image",
	"target": "image_cropper/cropper/input_image"
      },
      {
	"source": "image_cropper/cropper/output_image",
        "target": "color_camera_viewer/viewer/image"
      }
    ]
  }
}

without the changes the sample works fine.

With the following Gstreamer pipeline I’m able to get a downsampled video stream:

gst-launch-1.0 nvarguscamerasrc ! 'video/x-raw(memory:NVMM), width=(int)640, height=(int)480, format=(string)NV12, framerate=(fraction)30/1' ! nvvidconv flip-method=0 ! videoconvert ! 'video/x-raw, format=(string)I420' ! nvoverlaysink

However, when I try to include this pipeline in my Isaac application (as explained here or in this forum entry), I get the following error:

GST_ARGUS: Creating output stream
CONSUMER: Waiting until producer is connected...
GST_ARGUS: Available Sensor modes :
GST_ARGUS: 3264 x 2464 FR = 21.000000 fps Duration = 47619048 ; Analog Gain range min 1.000000, max 10.625000; Exposure Range min 13000, max 683709000;

GST_ARGUS: 3264 x 1848 FR = 28.000001 fps Duration = 35714284 ; Analog Gain range min 1.000000, max 10.625000; Exposure Range min 13000, max 683709000;

GST_ARGUS: 1920 x 1080 FR = 29.999999 fps Duration = 33333334 ; Analog Gain range min 1.000000, max 10.625000; Exposure Range min 13000, max 683709000;

GST_ARGUS: 1640 x 1232 FR = 29.999999 fps Duration = 33333334 ; Analog Gain range min 1.000000, max 10.625000; Exposure Range min 13000, max 683709000;

GST_ARGUS: 1280 x 720 FR = 59.999999 fps Duration = 16666667 ; Analog Gain range min 1.000000, max 10.625000; Exposure Range min 13000, max 683709000;

GST_ARGUS: Running with following settings:
   Camera index = 0 
   Camera mode  = 2 
   Output Stream W = 1920 H = 1080 
   seconds to Run    = 0 
   Frame Rate = 29.999999 
GST_ARGUS: Setup Complete, Starting captures for 0 seconds
GST_ARGUS: Starting repeat capture requests.
CONSUMER: Producer has connected; continuing.
====================================================================================================
|                            Isaac application terminated unexpectedly                             |
====================================================================================================
#01 external/com_nvidia_isaac_engine/engine/alice/tools/main(+0x65fc8) [0x556448bfc8]
#02 external/com_nvidia_isaac_engine/engine/alice/tools/main(+0xcfa88) [0x55644f5a88]
#03 external/com_nvidia_isaac_engine/engine/alice/tools/main(+0xcfd90) [0x55644f5d90]

The pipeline in my app.json file looks like this:

"feeder": {    
        "pipeline": {
          "pipeline": "nvarguscamerasrc ! video/x-raw(memory:NVMM),width=1920, height=1080, framerate=30/1, format=NV12 ! nvvidconv flip_method=0 ! videoconvert ! video/x-raw, format=I420 ! appsink name =   acquired_image"                                                                                                                                                                                          
        }                                                                                                                                                                                                   
      }                                                                                                                                                                                                     
    }

Any idea on why this pipeline is not working with Isaac?