EDIT: Can you send link to that page so I can see the css?
This is a bit of a shot in the dark, as I have only done this with adding image sizes but I am sure you should be able to alter the thumbnail crop position. Are 100% the image src is incorrect and the image isn’t being cut off by css?
function setup_image_sizes() {
set_post_thumbnail_size( 50, 50, array('center', 'center') );
//Or try
update_option( 'thumbnail_crop', array('center', 'center') );
//I am assuming the image size is called thumbnail but it might be different if it is created in the plugin
}
add_action( 'after_setup_theme', 'setup_image_sizes' );
Reference: https://developer.wordpress.org/reference/functions/add_image_size/