I'm experiencing the same issue from time to time across a number of WordPress sites - so I figure it's worth starting a conversation as Google doesn't seem to have much to say about this.
In a number of sites, at differnt times, using ACF Pro, certain data seems to go missing from the front-end. Simply resaving the post in admin and then refreshing on the front-end resolves the display issue - per post.
As this is happening in hundreds of posts on a brand new site this time, it's worth seeing if anyone has had this - and what they've done to resolve it. Finding each post amongst thousands is going to be too much effort to hunt and resave each from the admin panel.