Yep, that’s what I meant, but the post type should be defined when ACF is running the query, so that’s not the problem. At this point I’m not sure where to tell you to look. There are a few things you can check.
1) There is an error during the AJAX requests. Turn on WP debug and WP log and see if any php error happen during the query. This could happen when changing servers if the php version is different.
2) There is a pre_get_posts filter that interfering with the query. Unlikely if the code is the same on both servers, but you never know. You can try disabling any filters that you find.
3) There is and acf/fields/post_object/query filter https://www.advancedcustomfields.com/resources/acf-fields-post_object-query/ that’s interfering, again, unlikely if the code on both servers is the same. try disabling the filters.
