Resolved in: WPML Media Translation - next release (2.2.4)
If you have more than one custom field using the same name, and if they have different data, their values can be overwritten with the last data entered in the last used field. This happens if these custom fields’ translation options are set to “Translate”.
The issue comes from the Media Translation add-on plugin and will be fixed in the next release of WPML Media Translation plugin.
As a workaround you can go to the ../wpml-media-translation/classes/images-translation/ folder and edit the class-wpml-media-custom-field-images-translation.php file.
There, change the line:
update_post_meta( $post_id, $meta_key, $meta_value_filtered );
update_post_meta( $post_id, $meta_key, $meta_value_filtered, $meta_value );