Cannot change the SPO URL to a URL of an old site after changing the original sites URL

[JG-GP]

I needed to change the URL of a sharepoint site from .../sites/sitename to .../sites/sitename-public since we are using it for external only sharing. Then when I go to change the sitename of the internal site to the old name of the original site it gives me an error that I cannot use the sitename of .../sites/sitename because it already exists. 

My assumption is the original URL that I want to use is somenow cached and I cannot use it. 

[#2]

I've run into this before, you just need a little PowerShell magic: https://learn.microsoft.com/en-us/sharepoint/manage-site-redirects