I'm sorry for not coming back to you sooner. I've disabled the Spam Protect Factory extension.

When register more new users with you extension disabled, then I realised Expired URLs shows up on Registration in Redirect with the error code 301. For further information see: forum.joomla.org/viewtopic.php?f=706&t=9...1&p=3607799#p3607799

I will keep your Spam Protect Factory extension disabled until the 301 error code issue has been solved.