When we paste a value into a linked field Airtable attempts to either link the current record to a record in the other table with a primary field with that value, or it creates a record in the other table with a primary field with that value
In your "Members" table, the primary field appears to be the name, and in your automation you appear to be pasting the member's account ID value into the linked field, causing the creation of a new record in the "Members" table with the primary field value of the account ID
To get around this, you could try using the member's name, or the record ID of the member's record instead. You could also change the table layout of the 'Members' table instead, and make the account ID the primary field there