We have the same issue now, in version 5.3.1, in 2015. We did not register anything via the theme. We merely duplicated a section of field groups. What else can lead to this situation? It’s highly disconcerting that all field groups disappear, but the custom fields still show in the post screens. What else can we do? Thank you.
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users