After CW v2 upgrade, error 500 on existing wizard [edit: solution found!]

Environment

Discourse Version: 2.9beta10

Plugin Commit: FIX: straighten-out wizard-level subscription features · paviliondev/discourse-custom-wizard@12cd8ac · GitHub

Steps to Reproduce

  1. open https://cablogstaging.discoursehosting.net/w/growproblem
  2. see error 500

Example

The wizard was created on CW 1.x

https://cablogstaging.discoursehosting.net/w/growproblem

Logs

Console log:

Object { readyState: 4, getResponseHeader: getResponseHeader(e), getAllResponseHeaders: getAllResponseHeaders(), setRequestHeader: setRequestHeader(e, t), overrideMimeType: overrideMimeType(e), statusCode: statusCode(e), abort: abort(e), state: state(), always: always(), catch: catch(e), … }
application.js:83


Error while processing route: customWizard.index router.js:1065


Uncaught Error: Internal Server Error
    Ember 3
    trigger rsvp.js:182
    _onError rsvp.js:922
    invoke queue.ts:201
    flush queue.ts:98
    flush deferred-action-queues.ts:75
    _end index.ts:616
    end index.ts:298
    _run index.ts:667
    run index.ts:339
    d Ember
    error ajax.js:128
    jQuery 4
rsvp.js:44

OMG

after hitting save button once, the wizard now works. this step is crucial and should be mentioned during installation!