Cannot delete or edit a single term in a custom taxonomy, taxonomy name is wrong?

Question

I have created a custom taxonomy with the basic code below. I created a term called 'video' some time ago to test it. I created a few other terms today then noticed that I cannot delete or edit that first created term 'video'. It is grayed out and offers only the view link, which is a broken link. Oddly, using the correct permalink structure, the page for the 'video' term does display as expected.

I can create and edit other terms without any errors. There's also no errors anywhere else in the WP admin pages.

UPDATE:

After troubleshooting, I believe the issue is because I initially created the custom taxonomy with the name Purpose, but then changed it to purpose. Calling $object->taxonomy returns Purpose, while all the others listed in the admin panel return purpose.

How can I change this term's taxonomy from Purpose to purpose?

Here is the function that creates the taxonomy:

function post_purpose_taxonomy()
{
    $args = array (
        'labels' => array('name' => 'Purpose Tags', 'singular_name' => 'Purpose Tag'),
        'hierarchical' => false,
        'public' => true,
    );
    register_taxonomy('purpose', [ 'post', 'dvposts' ], $args);
}
add_action('init', 'post_purpose_taxonomy');

You can see that I register the taxonomy to both posts and the custom post type 'dvposts'.

Here is a snapshot:

Answer 1

Credit for this answer goes entirely to CodeMascot: Create and move terms for taxonomies

After troubleshooting, I believe the issue is because I initially created the custom taxonomy with the name Purpose, but then changed it to purpose at another time. Calling $object->taxonomy returns Purpose on the affected term, while all the others listed in the admin panel return purpose.

I strongly suspect that the taxonomy originally starting with a capital letter created a privileges issue, probably related to some to-lower-case method because some privileges were allowed. Once the taxonomy names matched perfectly, all issues were resolved.

After my troubleshooting determined that the taxonomy key of the term was incorrect, the question then became "How to change an existing term's taxonomy key"? The answer is that you must access the powerful and risky global $wpdb. This variable allows you to access and write the WordPress database directly. I added the following to the functions.php file, then refreshed a page two or three times, and the issue was resolved.

function the_dramatist_change_terms_taxonomy( $term_id, $future_taxonomy ){
    global $wpdb;
    $update = $wpdb->update(
        $wpdb->prefix . 'term_taxonomy',
        [ 'taxonomy' => $future_taxonomy ],
        [ 'term_taxonomy_id' => $term_id ],
        [ '%s' ],
        [ '%d' ]
    );
    return $update;
}

the_dramatist_change_terms_taxonomy(26,'purpose');

Now that the change has been made, I have removed the function from the functions.php file and $object->taxonomy returns purpose.