Dear @Ahn is there any news about that issue?
I am asking because I have some clients sites that are not working correctly.
I can re describe the issue to you.
It seems that in a website with WPML and metabox io installed, when you save / update a post with some specific metabox types like image_advanced, file_advanced the primary language is ok however in the same post in the secondary languages that specific files disappear. However the other types of metaboxes like texts, wysiwyg are intact.