If you can find information on the caching then it may be possible to help you. There must be some hook or function that is triggered or called to trigger the cache to be cleared. If you can find this out then you can probably add an acf/save_post action that will trigger the clearing. I don’t have experience with the caching mechanisms and I can’t help you any further without it. If you can find documentation on how to trigger the clearing I may be able to help you with that.
Please do not attribute the following opinion to the developers of ACF as this is a personal opinion of another user.
Your other option (being as rude as the suggestion from siteground) get hosting with better support. Sorry, but I find that an exceptionally rude suggestion from them. ACF is one of the most popular WP plugins and I’m sure you are not the only one with this issue so it would seem to me that they should be able to help their clients work around what sounds like it would be a common problem. Especially since, as I understand it, their service is built around hosing WP sites.
