Quite simply, the ‘wp_insert_post_data’ action is run BEFORE ACF save’s its data. This is why you get a ‘page load delay’.
Your best bet is to use the acf/update_value action to update the post title.
You can read about this action on the ACF docs page + there are already a few topics regarding updating a post’s title via an ACF field!
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users
Clients need flexibility. Developers need a repeatable workflow that doesn’t have a steep learning curve. See how digital marketing agency Noiza found both with Advanced Custom Fields in our latest case study.https://t.co/BxQAy6COJt