This error can occur when the contacts you are trying to merge are linked to a system user.
When trying to merge them, the system attempts to link one contact to another user, but a contact cannot be linked to more than one user. This results in an error, since the system does not allow this situation.
Such user-linked contacts should not be merged. If necessary, you can deactivate one of the users and rename the contact to avoid confusion.
Since deleting a user is not supported by the system by design, deleting a contact linked to such a user is also not possible.
If you have any further questions, please let us know, we would be happy to help. Thank you for choosing Creatio!
