Wordpress wp.media returns wrong image size in object

Question

I'm using the following code to open the WordPress media uploader in my plugin. The code works fine and returns the selected image.

  /* media*/

    var mediaUploader;
    $('#upload_image_button').click(function(e) {
      e.preventDefault();
        if (mediaUploader) {
        mediaUploader.open();
        return;
      }
      mediaUploader = wp.media.frames.file_frame = wp.media({
        title: 'Select Image',
        button: {
        text: 'Select Image'
      }, multiple: false });
      mediaUploader.on('select', function() {
        var attachment = mediaUploader.state().get('selection').first().toJSON();
        $('#background_image').val(attachment.url);
        

console.log(attachment.sizes);



      });
      mediaUploader.open();
    });

However when I look at the console - the custom image sizes (height and width) in the attachment.sizes are wrong, but the image, e.g. An image of 1024 x 1024 reports as 580x580 - but the filename clearly shows 1024x1024.

Any ideas on why this would be the case?

edit: Here is an image of all of the Image sizes in WordPress including 1 from the theme and one I added as a test.

As you can see the thumbnail , medium and full sizes are correct but large and the 2 added (using add_image_size( 'imagetest', 1200, 630, true ); // Hard Crop Mode) Are incorrect.

Thanks in advance.