No ideas at all. If these are basic text fields and not inside a repeater or something like that then I don’t see anything wrong with the code. I’m not seeing a problem on any of my own sites that do something similar. I just built a post type that gets the post title form an acf field using almost exactly the same code.
I would look at what could be interfering with it, like other plugins or other filters in the theme by switching themes and deactivating plugins.
