InternalLibraryError for a facilities C1

[lukehesluke]

We host an instance of OpenActive.NET, and have recently found that a C1 call, which previously worked, has stopped working. Here's the request (with the base URL stubbed out):

PUT <BASE_URL>/api/openbooking/order-quote-templates/2f792e86-0854-4b24-b567-06b160ef1437 HTTP/1.1

Content-Type: application/vnd.openactive.booking+json; version=1
X-OpenActive-Test-Client-Id: test
X-OpenActive-Test-Seller-Id: <BASE_URL>/api/identifiers/seller

{
  "@context": ["https://openactive.io/"],
  "type": "OrderQuote",
  "brokerRole": "https://openactive.io/AgentBroker",
  "broker": {
    "type": "Organization",
    "name": "imin"
  },
  "seller": "<BASE_URL>/api/identifiers/seller",
  "orderedItem": [{
    "type": "OrderItem",
    "position": 0,
    "acceptedOffer": "<BASE_URL>/api/identifiers/facility-uses/407/facility-use-slots/21925#/offers/0",
    "orderedItem": "<BASE_URL>/api/identifiers/facility-uses/407/facility-use-slots/21925"
  }]
}

The response:

{
  "@context": 'https://openactive.io/',
  "@type": 'InternalLibraryError',
  "description": 'The Opportunity @id within the response OrderItem must match the request OrderItem',
  "name": 'An unexpected exception has been thrown by an OpenActive SDK library or component.',
  "statusCode": 500
}

The Opportunity @id within the response OrderItem must match the request OrderItem - this implies that this is an issue within OpenActive.NET rather than a malformed request