I used a plugin (Post Duplicator by Metaphor Creations) to duplicate a field group. I’m thinking this does not work properly if it causes fields to have meta_keys that are not unique.
e.g. after duplicating a field group, and I want to change the field name of one of the fields, I end up with two fields that share the same meta_key like field_51e809fd7be5a, but one is “color” and the other is “material”.
I find that once used in editing the ‘material’ field the value does not get stored, because the input field uses the same meta key as ‘color’. it ends ups storing the data in a ‘color’ field.
Feature request to be able to duplicate a field group!
Please check out the http://www.advancedcustomfields.com/resources/getting-started/compatible-plugins/ page. On there, you will find a compatible post duplicator plugin!