After updating 1.4.3, there are problems
I tested the registration system on my portal.
With version 1.4.2, when I repeatedly created, deleted a user with the same data, the user's name was duplicated in the general list of users. And he was online in all his clones.
In version 1.4.3, when creating such a user, it does not receive rights to the forum, although the group has it registered. I can not change the group. About the change of the group everything passes without errors, but the band does not change.
You can register here https://dev.vavilova81k1.ru/
The Menu will display the Forum
Then delete the user and create with the same user name.
And again go to the forum.
I don't see wpForo registration form. And I can't say how the current registration form delete and create users. I'm really sorry but I'll not be able to support you in this issue. As far as I understand this plugin doesn't delete users clearly and the second user conflicts with old non-deleted old user data. I recommend after deleting a user, open your database > wpforo_profile table and check if the row with UserID of deleted user exists, if it's there just delete it. This is all I can help you in this situation.
Tom, thanks for the technical information, she helped me to determine the method of repair, a similar problem. It is necessary to put the correct user ID, in the table about which you wrote to me, because there is a user with the same name, but with a different ID.
The registration form on my website is general, not from your forum.
The address of her https://dev.vavilova81k1.ru/va-registration/
I use the Ultimate Member to create registration forms and access to various parts of the site. But when you delete yourself by the user, it is removed from the wordpress database, but there remains in the table of your users. What should happen with the user's messages in the forum if his account is deleted?