The issue of a JustGiving page not being linked to the correct contact will occur if an email address is assigned to an incorrect contact, resulting in a false link.
To fix this, please correct the address information against the contact records, then remove the page and re-upload the data. The page will then link to the correct contact.
If your JustGiving pages are brought in via the API please reach out to us via the Digital Assistant and provide us with as many details as possible so we can assist.