If the products were duplicated with bulk duplication in Translation Management they may have been created before the media images for the galleries were duplicated too. In that case the products would need to be updated with the images again.
Have you tried to update the media running in WPML >Media Translation the options to duplicate the media again? If not, please do this in order to be able to choose the images again from the media library.
After this you would need to update original products and translations to get the images copied again to the translated products.
For existing products you also can use the synchronization option in WPML > Support > troubleshooting page (link at the right bottom) and run the options to synchronize the taxonomies for media, products and pages.
I logged into the admin for a moment to check the issue and saw that you are still using WPML version 3.9.3.
Have you considered to update to WPML latest version 4.0.7?
As the last stable version before the mayor updates to WPML 4 was 3.9.4, I would also recommend to use that version.
In any case, please try it first on a staging site before updating on a life server.