If "ignore" was clicked during a merge in the past, these will not be recognized as duplicates.
To correct this, create the customer again. (Name and/or email + phone number) This way, along with the ignored suggestion, three duplicates exist.
The ignored suggestion will then be displayed.
Please note that merging customers cannot be undone and should therefore be carefully reviewed beforehand.
Simply click the X and merge.
After a successful merge, it is recommended to briefly check the remaining customer entry to ensure that appointments and contact details have been completely transferred.