What routing type and development model are you using? Are you able to reproduce the issue using e.g. the sample Dancing Goat project?
I just tried it using the Dancing Goat Core project and it works fine. I have a page with URL slug: /contacts
I changed the slug to be /contactsX
Former URL was created.
Then, I changed the slug back to /contacts
Second former URL is created.
Using incognito window - I am not getting a redirect loop, the page is displayed just fine.