Same as #3877 unsesolved also with different browser

Testdriving event online registration

Selecting event and then select test driving. The next page shows an error message

Oops. It looks like you are already registered for this event. If you want to change your registration, or you feel that you've gotten this message in error, please contact the site administrator.

This is, because the logged in user has already created a test online registration for his e-mail. If I have not created a test registration for the user currently logged in, then truely the registration page shows up and I can change the e-mail at whish to create as many test registration I wish.