That’s not a question I can answer. I will mark the question for the developer to look at if he has time, but as a general rule he doesn’t actually visit this forum on a regular bases. This is a forum for ACF users to get help from other ACF users.
But like I said above. If I was having this problem I would do my own caching of the field group I was building using PHP so that I was not actually rebuilding the field group on every page load. ACF is built to take advantage of WP core functionality and core does not include persistent caching.
