New answers tagged save-post
My approach to this problem is to access "raw" metadata directly from $_POST[metabox_id] in wp_insert_post_data filter hook. I do admit that this approach is suitable more for my project where posts are generated entirely out of metadata and need to be re-rendered everytime. Tough someone might find it useful.
This seems to be a core bug, spotted at 4.5 as well. Although documentation implies otherwise, you can not select in practice terms of non hierarchical taxonomies with the "checkoxed" metabox, the only working option is the "tag" style metabox.
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