Hi @davred
I’ve just tested it on my installation but failed to reproduce the issue. Maybe there’s a conflict on your site. Could you please try to reproduce the issue on one of the WordPress’ stock themes (like Twenty Sixteen) with only ACF activated? If it disappears, then you can activate the theme and plugins one by one to see which one causes the issue.
Also for a new post form, you should set the post_id to “new_post”. This page should give you more idea about it: https://www.advancedcustomfields.com/resources/using-acf_form-to-create-a-new-post/.
Thanks 🙂
