Linking a Contact to a Customer using the SOAP API

Hello, I’m having an issue with linking a customer object to a pre-existing contact when creating a new customer within the SOAP/SuiteTalk API using the Mulesoft middleware.

I’m successfully creating the contact object earlier, and then trying to use that internal ID to link that contact object to the newly created customer object. The relevant part I’m posting within the customer object (just hardcoding the internal ID in order to get it running):

contactRolesList:

   {

      contactRoles:

         [

            {

               contact: {

                  "type": "CONTACT",

                  internalId: '74335',

               },

               role: {

"type": "CONTACT_ROLE",

                  internalId: ‘-10’,

               }   

            }

         ]

   }

When I attempt to upsert the customer object this way, I don’t get any errors in the integration role execution log, but the contact is never linked. If I try to upsert a second time, I get an error with the format: Unable to find a matching line for sublist contactroles with key: [contact] and value: [74335]. even though a contact object with that internal ID clearly exists.