I have written a post and then deleted it and then rewritten it so making a mess.
Now, my original post is entitled "discussion part 1" and I have the purpose to write other posts entitled "discussione part 2" and "discussion part 3".
However, due to my mess, the post slug is currently "discussion-part-1-2". I have tried several time to rename it to "discussion-part-1" by editing the slug text box in edit page mode, but every time I confirm, the slug returns to be "discussion-part-1-2".
So, how can I force slug renaming?