New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({
  actions: {
    addToOutlet: function(name) {
      console.log('--> render outlet  ' +name); 
      this.render(name, {
        into: 'application',
        outlet: 'modal'
    	});
    },
    removeOutlet: function() {
     console.log('  disconnecting outlet');  
        this.disconnectOutlet({
        outlet: 'modal',
        parentView: 'application'
      });
    }
  }
});

templates.application.hbs

<h1>Disconnect outlet error Ember 2.6</h1>
<br/>
1. Click render 1
<br/>
2. Click Disconnect outlet
<br/>
3. Click render 2
<br/>
<br/>
{{outlet}}

<button {{action 'addToOutlet' 'option1'}}>
Render 1
</button>
<br/><br/>
<button {{action 'removeOutlet'}}>
Disconnect outlet
</button>
<br/><br/>
<button {{action 'addToOutlet' 'option2'}}>
Render 2
</button>
<br>
<br>

{{outlet 'modal'}}

templates.option1.hbs

Rendered option 1

templates.option2.hbs

Rendered option 2

twiddle.json

{
  "version": "0.9.2",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.6.0",
    "ember-data": "2.6.0",
    "ember-template-compiler": "2.6.0"
  }
}