How reproduce

• Go to the demo https://demo.ametys.org/projet/projet-d-exemple-public/fr/members.html
• Add member example: votreadresseemail@ametys.org
• subscribe to the project from the email
• choose a first and last name when registering
  We see that the person is registered
• re-invited a person with another email address exmple : votreadresseemail+15@ametys.org
• Sign up again from the email link
• register with the same first and last name as the first registration

The person is registered but does not appear in the group members

It is therefore impossible for a person to have two registrations with two different emails