GraphQL query in NodeJS fails with "There was a problem with the requested skill's response"

The below GraphQL request is based on this tutorial and the Alexa NodeJS HelloWorld boilerplate. After running the invocation name Alexa returns "There was a problem with the requested skill's response" . How to fix this issue?

const Alexa = require('ask-sdk-core');

const { GraphQLClient } = require('graphql-request');
const GRAPHQL_ENDPOINT = 'https://api.graph.cool/simple/v1/cixos23120m0n0173veiiwrjr';
const graphQLClient = new GraphQLClient(GRAPHQL_ENDPOINT, { })
const helloWorldQuery = `
    {
      Movie(title: "Inception") {
        releaseDate
        actors {
          name
        }
      }
    }
  `
  
const LaunchRequestHandler = {
  canHandle(handlerInput) {
    return handlerInput.requestEnvelope.request.type === 'LaunchRequest';
  },
  handle(handlerInput) {
    const speechText = 'Welcome to the Alexa Skills Kit, you can say hello!';

    return handlerInput.responseBuilder
      .speak(speechText)
      .reprompt(speechText)
      .withSimpleCard('Hello World', speechText)
      .getResponse();
  },
};

const HelloWorldIntentHandler = {
 canHandle(handlerInput) {
 return (
      handlerInput.requestEnvelope.request.type === 'IntentRequest' && handlerInput.requestEnvelope.request.intent.name === 'HelloWorldIntent'
    );
  },
 async handle(handlerInput) {
 const response = await graphQLClient.request(helloWorldQuery);

 const speechText = `Hello World ${response}`;

 return handlerInput.responseBuilder
 .speak(speechText)
 // .withSimpleCard('GraphQL Query', speechText)
      .getResponse();
  },
};