I'm using the latest version of MetaBox (5.3.9).
I've configured a "Post" field using the select advanced option.
I've set up "clone", "clone_sort" and "ajax" to true, with a query args for a custom post type and a custom taxonomy, as you can see:
The problem is that the search function of the select2 library is not working.
When typing in the search bar, it always says "no results found".
It is working when the 'post_type' arg is set to 'post', but still, it's a bit buggy: it first shows "no results found", and after 5 seconds the result is shown.