500 error when attempting to use form wizard with js = 'ajax'

Has anyone successfully created a ctools wizard form that moves between steps with ajax? If so, can documentation be provided on the steps needed to implement?

Issue:
When attempting to move between steps on a wizard form with ajax enabled, a 500 error occurs when hitting the "next" button.
Drupal\Core\Form\FormAjaxException: in Drupal\Core\Form\FormBuilder->buildForm() (line 334 of /var/www/html/core/lib/Drupal/Core/Form/FormBuilder.php).

To reproduce:
When i was attempting to make this work, I simply copied the ctools_wizard_test module into my modules directory and modified the routing.yml. I added js: 'ajax' to the ctools.wizard.test.step and ctools.wizard.test routes after finding line 77 of WizardFormController.php that seemed to indicate adding that info to the routing would cause the form to work via ajax.

ctools.wizard.test:
  path: '/ctools/wizard'
  defaults:
    _wizard: '\Drupal\ctools_wizard_test\Wizard\WizardTest'
    _title: 'Wizard Test'
    tempstore_id: 'ctools.wizard.test'
    machine_name: 'WizardTest'
    js: 'ajax'
  requirements:
    _access: 'TRUE'
ctools.wizard.test.step:
  path: '/ctools/wizard/{step}'
  defaults:
    _wizard: '\Drupal\ctools_wizard_test\Wizard\WizardTest'
    _title: 'Wizard Test'
    tempstore_id: 'ctools.wizard.test'
    machine_name: 'WizardTest'
    js: 'ajax'
  requirements:
    _access: 'TRUE'

I was intially attempting to get this whole thing to work within a modal so i additionally created a new route and controller that simply outputs a button that opens the ctools.wizard.test route in a modal. This does cause step one of the form to load in a modal, but the same error occurs when attempting to hit "next".

I have tried this with core versions 8.2.7 and 8.3.0.

At this point, im not sure if there is a bug or if I am missing something required to make this work correctly. Any assistance would be greatly appreciated.