Bug? In front end form, "add new", checkbox tree display

I think this is a bug but am not sure. I believe that the result of using the new "Add New" displays poorly if the field is displayed using "checkbox tree".

• In Meta Box, create a CPT and an associated taxonomy. The taxonomy must be hierarchical.
• Seed the taxonomy with some terms. Make some of them children.
• Create custom fields for the CPT. At least one field should be for the associated taxonomy, type "taxonomy", and display type should be "checkbox tree".
• On a page, set up a shortcode mb_frontend_form to create a new custom post.
• View the page, and see that the checkbox tree shows existing hierarchical terms. Click the taxonomy's "add new" button. Create a new taxonomy term. Return to the main form.
• See that the new term appears, but it appears multiple times.

The taxonomy term has actually only been created once. This seems to be a display problem with a checkbox tree.

If you can't reproduce it, I would appreciate your looking at a test site I can give you access to.

Thank you.