Thanks John. The theme caused the issue.
I used the filter “wp_insert_post_data”, which causes ACF to fail. I used the filter with a priority of 99, maybe this is to high (didn’t tested it).
One ugly thing I noticed while experiencing this problem was that ACF creates multiple columns inside the database.
Is there a plan to add a feature to remove all ACF-data stored in the database? When deinstalling the plugin, acf leaves a huge data mess. The same problematic shows up when renaming fields.
