I created a custom taxonomy to go with my custom post type, for this example we will say its called "alpha bravo". I also have the term "charlie delta" under this taxonomy. They are attached to my custom post type "foxtrot".
When I go to Alpha Bravo under my Foxtrot in admin I can see and add terms no problem. But when I click on Charlie Delta I get "Invalid taxonomy" with the url: /wp-admin/edit-tags.php?action=edit&taxonomy=alphabravo&tag_ID=46&post_type=foxtrot.
If I change the URL to /wp-admin/edit-tags.php?action=edit&taxonomy=alpha%20bravo&tag_ID=46&post_type=foxtrot then it works just fine. Not sure if this is an error due to CPT UI or a glitch WP core. Thought I would bring it up in case you can fix it.