the icl_make_duplicate filter intentionally disables this because of the following bugs (quoted from the source)
always translate independately to avoid many many bugs!
– translation post gets a new key (post_name) when origional post is saved
– local json creates new files due to changed key
Edit: This bug probably belongs over at WPML as they are the ones setting a new key when the fieldgroup is saved. https://wpml.org/forums/topic/wpml-acf-field-groups-are-not-duplicating-properly/
