Sinon.restore not working for stubbing and testing AWS functions

So I'm trying to write a few tests for testing an AWS wrapper library that I have been writing. The tests are running individually without any issues, but won't all run as one 'describe' block.

const AWS_REGION = 'eu-west-2';

const aws = require('aws-sdk');
const chai = require('chai');
const expect = chai.expect;
const sinon = require('sinon');
const sinonChai = require('sinon-chai');
chai.use(sinonChai);

// These help:
// https://stackoverflow.com/questions/26243647/sinon-stub-in-node-with-aws-sdk
// https://stackoverflow.com/questions/61516053/sinon-stub-for-lambda-using-promises
describe('SQS Utilities Test', () => {

  afterEach(() => {
    sinon.restore();
  });

  it('should add to SQS', async () => {
    sinon.stub(aws.config, 'update');

    const sqs = {
      sendMessage: sinon.stub().returnsThis(),
      promise: sinon.stub()
    };
    sinon.stub(aws, 'SQS').callsFake(() => sqs);

    // these use the above stubbed version of aws
    const AWSUtilities = require('../index').AWSUtilities;
    const awsUtilities = new AWSUtilities(AWS_REGION);
    const response = await awsUtilities.postToSQS('https://example.com', { id: 1}, 'chicken');

    expect(sqs.sendMessage).to.have.been.calledOnce;
  });

  it('should get from SQS', async () => {
    sinon.stub(aws.config, 'update');

    const sqs = {
      receiveMessage: sinon.stub().returnsThis(),
      promise: sinon.stub()
    };
    sinon.stub(aws, 'SQS').callsFake(() => sqs);

    // these use the above stubbed version of aws
    const AWSUtilities = require('../index').AWSUtilities;
    const awsUtilities = new AWSUtilities(AWS_REGION);

    const response = await awsUtilities.getFromSQS('https://example.com');
    expect(sqs.receiveMessage).to.have.been.calledOnce;
  });

...

What I noticed, is that in the second test, the error I am getting is sqs.receiveMessage is not a function, which means that the second test is using the sqs object from the first test (I can further verify this as the error changes if I add receiveMessage to the first test sqs object).

Is this a bug in sinon restore, or have I written something incorrectly? Here is the whole library: https://github.com/unegma/aws-utilities/blob/main/test/SQSTests.spec.js