Unable to add new Authorized Redirect URI because of specific subdomain

So I have a web application I use for volleyball event management called Ball Out Volleyball, and I have a "Login with Google" button to make signing up easier. I have different subdomains for the different event organizers that also use it (www, swervcup, championscup, etc). I am having an issue when trying to set up and add my newest organizer, using the subdomain "expansion.balloutvolleyball.com", and get the error below, and does not save the new line:

The request has been classified as abusive and was not allowed to proceed

I tried using several other subdomain words, and they all work. I tried misspelling expansion with several iterations, and it works. I even tried removing the word expansion from the subdomain, and put it later in the URI, and it worked. So it seems that Google has an issue specifically with the word "expansion" only in the subdomain of the URI.

Any ideas, Google Gurus? 

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