_thumbnail_id can only have one value, you need 2 fields for 2 images or you need _thumbnail_id (which is the default meta_key for the WP featured image) for one and another field name for the second image.
Welcome
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users
We use cookies to offer you a better browsing experience, analyze site traffic and personalize content. Read about how we use cookies and how you can control them in our Cookie Policy. If you continue to use this site, you consent to our use of cookies.