Outbound Campaign API 400 Error on Custom Data Payload

Could someone explain why this setting causes a 400 Bad Request when updating an outbound campaign via the platform API? The error indicates the custom data structure is malformed, yet it validates correctly in the schema validator.

We are building a multi-org integration that requires dynamic campaign configuration. When pushing a campaign update to the POST /api/v2/outbound/campaigns/{campaignId} endpoint, the response returns a 400 error with the message: Invalid custom data format. Expected array of objects.

The payload being sent is structured as follows:

{
 "customData": [
 {
 "key": "partner_id",
 "value": "12345"
 }
 ]
}

According to the documentation:

“Custom data must be provided as an array of key-value pairs where both keys and values are strings.”

This matches our structure exactly. We are using the Genesys Cloud SDK v1.0.10 in a Node.js environment. The issue persists across multiple orgs, suggesting it is not an org-specific configuration issue. Has anyone encountered similar validation failures with the outbound campaign API? We need to resolve this to proceed with our AppFoundry integration deployment.