Sorry to be the guy who necros an old post like that but as of September 2016 the issue still persists. I am running ACF 5.4.4, WPML 3.5.1.1 and WordPress 4.6.1 so pretty much the bleeding edge on all fronts. I am experiencing the exact same bug as described above – when duplicating a field group from the main language to another I get a separate translation even though I check the Duplicate tickbox. This can lead to having a hard to diagnose discrepancy between field group definitions in different languages especially when working with a team of people. The groups need to be duplicates to remain up to date with the main language.
Why is this issue marked as “solved”? Let’s keep this thread alive people, this is an important feature @elliot
