Duplicated site has same URL as site copied from

I am working on a multisite installation with a primary site in English and two duplicate sites in Spanish (/es) and Japanese (/jn). We want to create a new duplicate German duplicate site within the network at /de.

When I duplicate the site, I select one of the language sites (/es) to duplicate. For the address of the new site I enter “de” (since the prompt already provides mysitenamehere.com/).

The duplicated site ends up with the same siteurl and home address as the site it was copied from. Even though in My Sites, the site is called mysitenamehere.com/de, and when you edit the site, the Site Address (URL) field says mysitenamehere.com/de, the actual siteurl and home fields say mysitenamehere.com/es. When you click “Visit”, it takes you to mysitenamehere.com/es. The admin panel is at mysitenamehere.com/es/wp-admin. And so on.

What is happening that the duplication is not actually putting my site in a new directory?