PATCH /conversations/voice/{id} transfer to queue returns 409 Conflict

Attempting to transfer an active voice interaction to a specific queue using PATCH /api/v2/conversations/voice/{id}. The payload includes the to object with type set to queue and the correct id, but the API responds with a 409 Conflict. The documentation implies this should work for queue-to-queue transfers, yet the error suggests a state mismatch. Here is the request body:

{
 "to": {
 "type": "queue",
 "id": "queue-id-here"
 }
}

The interaction is currently in connected state. Is there a missing header or a specific sequence required before patching the target?