I’m not familiar with magic fields but it’s likely that it uses a underscore for the keys and the plugin ignores thoses fields ( with some exceptions)
You either can add the keys to the ‘whitelist’ on the plugin menu oage or, if you don’t know the keys, the only way is to open ThreeWP_Broadcast.php, scroll to the bottom and find the function
is_custom_field_valid
uncomment / delete / replace the function body with return true;
