I’m having a similar problem – I’m using plain wordpress, with WordPress Access Control and New User Approve. I set 3 security questions, and on the configuration page there have been no correct answers since the one I answered myself to test. However, I am still getting many user registrations per day, so they must be bypassing WangGuard somehow. If I go on and manually try to create an account it prevents me, so the security question is working in some ways, but I assume there must be another way in.
My wp instance is at https://www.greenwich-academy.com
Thanks,
James