Thanks for the reply Nicholas.
I rely on Admin Tools (AT) to protect both Joomla and WordPress sites I maintain, which is why I posted this ticket in the first place. Believe me it was with great reluctance that I unpublished it, but as this was the only mention of a solution to the issue, I used it. The client already had to deal with 38-new registrations that didn't complete because of the issue, and I wanted to avoid more.
Here is the ticket I found on the Community Builder (CB) website #333894
I am unconvinced that AT is the cause of this issue, as I have another site that includes both CB and AT, which doesn't have this issue, but I needed a solution.
I am happy to provide more information or access is that will help solve this issue.
Thank you.
Ed