Problem with Shibboleth login: email conflict

What steps does it take to reproduce the issue?
Create 2 builtin user accounts in Dataverse, with username test_user, test_user1 with email address not equal to test_user@testemail
Login via Shibboleth with the email address test_user@testemail
Accept the term and click the create account button

• When does this issue occur?
  When new user login via Shibboleth

• Which page(s) does it occurs on?
  When user login via Shibboleth and create new account

• What happens?
  After clicking the Create Account button, the page keeps loading but cannot create a new account

• To whom does it occur (all users, curators, superusers)?
  User Login via Shibboleth

• What did you expect to happen?
  The user can create a new account successfully with username test_user2

Which version of Dataverse are you using?
Dataverse v5.5

Any related open or closed issues to this bug report?
https://groups.google.com/g/dataverse-community/c/Jo7Uhn5lDe8

Screenshots:

No matter the issue, screenshots are always welcome.

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No file or test is named. Start by reproducing the Shibboleth login and account-creation flow with the two conflicting builtin accounts, then trace the account-creation path handling the existing email. Done means a new user can create the expected test_user2 account successfully.