joselov

I found the solution by myself.
To anyone that is having the same problem, rather than remove_meta_box and add_meta_box, simply include this:

// Global the $wp_meta_boxes variable (this will allow us to alter the array)
global $wp_meta_boxes;

// Then we make a backup of your widget
$my_widget = $wp_meta_boxes['dashboard']['normal']['core']['{widget id here}'];

// We then unset that part of the array
unset($wp_meta_boxes['dashboard']['normal']['core']['{widget id here}']);

// Now we just add your widget back in
$wp_meta_boxes['dashboard']['side']['core']['{widget id here}'] = $my_widget;

inside a function and ‘add_action’ with ‘add_meta_boxes’ hook.

I find this here.

I just found a solution.
The problem was I had a function to prevent drag of metaboxes and that was generating the conflict. This was made a conflict with the ‘add new terms’ function to taxonomies (hierarchical or not).