I have a custom post type called "services".
I create a category of "services" called Copacabana and copacabana slug is generated.
Then I create a subcategory of a regular category (post_type = category, not the post type "services") with the same name, and she records the copacabana slug of my custom post type again.
When I change the category slug from the subcategory, it changes my post_type "services" as well, because it acts like the same thing.