Problem splitting tests using Jest

This is our config to split tests:

- &test
  name: Run Tests
  command: |
    TESTFILES=$(circleci tests glob "./packages/main/src/**/__tests__/*.(test|spec).(js|ts|tsx)" | circleci tests split)
    echo "All test files:"
    circleci tests glob "./packages/main/src/**/__tests__/*.(test|spec).(js|ts|tsx)" | xargs -n 1 echo
    echo "This job test files:"
    circleci tests glob "./packages/main/src/**/__tests__/*.(test|spec).(js|ts|tsx)" | circleci tests split | xargs -n 1 echo
    echo "Running tests:"
    JEST_JUNIT_OUTPUT="./test-results/jest/results.xml" yarn jest --maxWorkers=4 --coverage --forceExit --ci ${TESTFILES}
    bash <(curl -s -t $CODECOV_UPLOAD_TOKEN

    <<: *defaults
    parallelism: 2
      - attach_workspace:
          at: ~/app
      - restore_cache: *restore-mongodb-binaries-cache
      - run: *copy_env
      - run: *test
      - restore_cache: *save-mongodb-binaries-cache
      - store_test_results:
          path: ./test-results

Use use the following docker to test

- image: entria/node-ci:0.1.12
- image: circleci/redis:4.0.9

The time to run in 1, 2 or 4 is the same for us