@princeofabyss sorry for not replying to this sooner, but when saving any post that has acf fields on it you should actualy use the acf/save_post hook with a priority > 10. This ensures that any changes you make happen after ACF has run. ACF runs with a default priority of 10 on the generic save_post hook and if you use the default priority as well it will be a tossup as to which will happen first. This has a lot to do with when the actions are added and that has to do with the load order of files and this load order can change in some cases.
