Agent Scripting API 400 on BYOC Trunk Context Injection

Quick question about the Agent Scripting API. POST /api/v2/interaction-callbacks/agent-scripting returns a 400 Bad Request when attempting to inject custom SIP headers from our Singapore BYOC trunks into the scripting context. The payload validates locally, but the service rejects the carrier-specific metadata mapping. Is there a known limitation on passing BYOC trunk attributes into the scripting engine via this endpoint?