If you have two files or folders or categories or whatever with the same name, you confuse the computer. It can’t complete the task you ask it to do. Back in the old days, the computer would just crash (temper tantrums computer style.) Now a days, the programmers know that they have to keep that from happening, so, they prevent the user from duplicating names that could conflict.
But, then there is the user. No matter how many traps you set to make sure that there are no errors, there is always that something you didn’t think of. And, last week, a new one popped up that I hadn’t seen before. A WordPress Testimonials category page works fine, but when you click on the titles, some of them go to URL not found … and others work just fine. And, it turns out that there are two Testimonials categories.
This problem is very weird because, per paragraph 1, the WordPress core software prevents there being two categories with the same name by adding a -2 to the “slug” if a user creates a second category with the same name. The actual name of the category is just a label. The real name that WordPress uses is the slug. So, there is a testimonials category and there is a testimonials-2 category.
So, now it’s a matter of finding a pattern …