I didn’t figure out what was causing this problem, however, I did fix it.
The first thing, go into the categories.
Administration >> Posts >> Categories
Rename the category which has the problem to “Kansas City Royals1” (any name not used by another category will be fine) and rename the slug to “kansas-city-royals1”
Next, create a new category with the name you wanted originally, ie “Kansas City Royals” and make sure the slug is what you originally wanted “kansas-city-royals”
Now, change the default post category to the one your just created.
Administration >> Settings >> Writing >> “Default Post Category” >> Select: Kansas City Royals
Next, go back to categories and delete your old/malfunctioning category. When you delete your old category, all the posts in that category will be moved into the “Default Post Category”.
Lastly, go back and change your default category back to what is was before. Also, make sure that you make the necessary changes to your theme where the old category was called (if applicable).
NOTE: If your posts had multiple categories, the malfunctioning category will simply be removed from the relevant posts, and your new category will not be added to them. In this case, it would be best to view all articles in the old category and edit each post to include the new category before deleting the old category.
