This is an known issue and is due to the way that WP saves values when you click the “preview” link. WP does not submit custom fields when you do this. While the frustration it causes is understandable, There really isn’t any way that has been found to alter this behavior in WP.
I’ve done some further testing and it looks like there’s also an issue when the page is saved as a draft.
Basically hitting preview whilst the page is a draft is borked. I have to hit ‘save draft’ and then preview to see the changes. It is completely unworkable to have to publish a page first as I’m using flexible content fields as a page builder.
I’ve tried the work-around in the post but it dates back to 2013 and doesn’t seem to be working.
2022 was a big year for Advanced Custom Fields, with more capabilities, a new generation of ACF Blocks, a refreshed UI, and a new home. Our year in review post looks at advancements we’ve made and offers a glimpse of the future. https://t.co/HahJUCcyH4