Adding Phone Number & Linking to Relationships

Using the Users phone create endpoint (https://developer.sky.blackbaud.com/docs/services/school/operations/V1UsersByUseridPhonesPost), I can create the phone number for the user as is expected. However, I cannot get the linking functionality to work. Below is an example post URI & Body (I replaced the name and user IDs out with dummy data). It will create the phone number record for the user but will not link it. I verified that the relationship already exists, the user to be linked with already has the phone number attached to their user record, and that all the information is correct.

URI: https://api.sky.blackbaud.com/school/v1/users/3154032/phones

BODY

{
"links": [
{
"id": 331,
"shared": true,
"shared_relationship": "Spouse",
"shared_user": "John Doe",
"type_id": "Home",
"user_id": 5942642
}
],
"number": "(555) 555-5555",
"type_id": 331
}

Would someone be able to verify that the endpoint is working as it is supposed to?