Hi,
when I create a new field, it gets stored in wp_posts with post_type acf_field. It also has a post_name. And here we have a bug.
When I create a new field, the post_name is something like
field123abc
However, it should be
field_123abc
This bug makes it impossible to save data into fields. And also prevents the searcher from searching. (ref: https://support.advancedcustomfields.com/forums/topic/search-field-finds-nothing/ )
OK nevermind, error on my end. Had a filter on sanitize_title which killed the underscore.
Sorry for the trouble I caused 🙁