If this occurs, check the learner's profile via Aptem Console. If the 'Landline' number contains a comma or any special character that is not a supported format, this issue will arise.
After removing any invalid special characters, you can update the learner's profile.
Please note that the Aptem system has validation in place to prevent the entry of special characters in this field, so it is not possible to enter an invalid line number via the UI. However, please be mindful of the format when creating entries via the API.