After upgrading to 5.5.4 something strange started to happen. Each time a post is saved a duplicate of that post is created. The duplicate has the same title, but all fields are empty. The source post looks fine and all changes are saved properly.
It seems to be related to the flexible content field because it happens only to these posts that have a flexible content field assigned.
Sorry for providing so few details, but a bug seems to be major, so I wanted to report it asap. If you want I can send you a db dump and ACF JSON export.
ACF is the only plugin I use. I use a custom theme, built by myself, there’s no “magic” in the theme, no custom filters applied, etc, so I’m pretty sure that it’s an ACF bug.
I’m having the same issue… it seemed to be fine until I updated to 5.5.4 today. I did register a new custom post type today, so I thought maybe somehow I had an issue because of that… but because someone else is having the same problem – it seems its an ACF issue.
