Dynamic Segment Bug

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
}

router\.js

import EmberRouter from '@ember/routing/router';
import config from './config/environment';

const Router = EmberRouter.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('parent', { path: '/parent/:upc' }, function() {
    this.route('child-sibling');
  });
  this.route('parent-sibling');
});

export default Router;

routes.parent-sibling\.js

import Route from '@ember/routing/route';

export default Route.extend({
  async model() {
    await new Promise((resolve) => {
      setTimeout(resolve, 2000);
    });
  }
});

routes.parent.child-sibling\.js

import Route from '@ember/routing/route';

export default Route.extend({
  async model() {
    await new Promise((resolve) => {
      setTimeout(resolve, 2000);
    });
  }
});

routes.parent.index\.js

import Route from '@ember/routing/route';

export default Route.extend({
});

routes.parent\.js

import Route from '@ember/routing/route';

export default Route.extend({
});

templates.application\.hbs

<h1>Welcome to the Dynamic Segment Bug Demo</h1>
<br>
<br>
To recreate:
<ol>
  <li>open your browser's console</li>
	<li>click on "Parent"</li>
	<li>click on "Sibling"</li>
  <li>before "Sibling" loads, click on "Child 2"</li>
  <li>wait 2 seconds, you'll see this error in the console: Uncaught (in promise) Error: You must provide param `upc` to `generate`.</li>
 </ol>
<br>
<br>
<LinkTo @route="parent" @model="123456">Parent</LinkTo>
<LinkTo @route="parent-sibling">Sibling</LinkTo>
<br>
<br>
{{outlet}}
<br>
<br>

templates.parent-sibling\.hbs

<h2>Sibling</h2>

templates.parent.child-sibling\.hbs

<h3>Child 2</h3>

templates.parent.index\.hbs

<h3>Child 1</h3>

templates.parent\.hbs

<h2>Parent</h2>
<br>
<br>
<LinkTo @route="parent.index">Child 1</LinkTo>
<LinkTo @route="parent.child-sibling">Child 2</LinkTo>
<br>
<br>
{{outlet}}

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}