Issue with 'Find a document by path or GUID

I am having problems running the connector.

When using the correct Document GUID (either with or without the curly brackets) The connector fails with a 'BadGateway' error.

    "code": 502,
    "source": "uk-001.azure-apim.net",
    "clientRequestId": "bf53866f-0f29-4393-9b77-17350fb878c7",
    "message": "The response is not in a JSON format.",
    "innerError": "Cannot read server response."
  }
}, clientRequestId: bf53866f-0f29-4393-9b77-17350fb878c7

If I enter an incorrect GUID the connector returns a 'Document NotFound' error as expected - although the full error does not seem right:-

"statusCode": "notFound",

"error": {
"message": "Folder with path '' not found."
The connection is working as it is using the same values as other Document Creation and modification connectors which are running ok.
Has anyone else had success with this connector?