How is the modal loaded? Is it a div inserted into the page? Is it in an iFrame? The problem is that the needed JS for the fields you mention isn’t being loaded because the fields are loaded later.
I just found this older topic where the developer answer this, let me know if it still works. https://support.advancedcustomfields.com/forums/topic/using-acf-form-in-ajax-call/, or is this what you’re referring to.
If it’s still not working then make sure you’re calling `acf_form_head()’ and ‘wp_footer’ in the right places, these are other causes for things not working correctly.
