Wrong aspect ratio for some avatars

When I generate a video through the API, with some avatars, the generated video has a incorrect aspect ratio.

Here is an example of request body which fails (avatar: chad in blue shirt, voice: pleasant pete):

{
  "video_inputs": [
    {
      "character": {
        "type": "avatar",
        "avatar_id": "chad_expressive_20240910",
        "avatar_style": "normal"
      },
      "voice": {
        "type": "text",
        "input_text": "Welcome to the new era of video creation with HeyGen! Simply type your script to get started!",
        "voice_id": "928c92b0b59b404982e0e586874398b5"
      }
    }
  ],
  "dimension": {
    "width": 1280,
    "height": 720
  }
}

Is something wrong? I expect the avatar to have a "correct aspect ratio" and be cropped if necessary.