I have a customer who appears twice in the customer list. One account is linked to their profile, which I can find in the admin page directories. The other account seems to be an unaccepted invite. See the image for reference.

The customer can supposedly log in from both accounts and create issues separately.
Both profiles have the same email and username, making them identical. This causes confusion because he can't see the tickets from one account in the other. How can I fix this?
I want to keep the account that's in the directory and delete the other one, but I'm not sure how to do it.