Angular2 router appends component instead of replacing it

Question

I have an Angular2 application with one router outlet that displays different components depending on which link is clicked in a side menu.

The markup for the main component containing the <router-outlet> looks like this

<div *ngIf="authenticated == false">
  <app-login></app-login>
</div>
<div *ngIf="authenticated">
  <div class="page home-page">
    <header class="header">
      <app-navbar></app-navbar>
    </header>
    <div class="page-content d-flex align-items-stretch">
      <div class="sidebar-container">
        <app-sidebar-menu></app-sidebar-menu>
      </div>
      <div class="content-inner">
      <app-page-header></app-page-header>
        <div id="sub-content">
          <router-outlet></router-outlet>
        </div>
        <app-footer></app-footer>
      </div>
    </div>
  </div>
</div>

If I click the Demo link, the demo component is rendered, but if I then click the Home link, the home component is rendered above the demo component in DOM. Clicking them a few times will result with a DOM like this

<div _ngcontent-c0="" id="sub-content">
    <router-outlet _ngcontent-c0=""></router-outlet>
  <app-home _nghost-c6="">...</app-home>
  <app-demo _nghost-c7="">...</app-demo>
  <app-home _nghost-c6="">...</app-home> <!-- Why so many here? Should be just either one <app-home> or <app-demo>  -->
  <app-demo _nghost-c7="">...</app-demo>
  <app-home _nghost-c6="">...</app-home>
  <app-demo _nghost-c7="">...</app-demo>
  <app-footer _ngcontent-c0="" _nghost-c5="">...</app-footer>
</div>

The routes are defined as

export const router: Routes = [
    { path: 'demo', component: DemoComponent, canActivate: [AuthGuard] },
    { path: 'home', component: HomeComponent, canActivate: [AuthGuard] }
]

How come that the <router-outlet> doesn't replace the component, but instead adds another "instance" of the component when switching between the routes?

Answer 1

By using the method of elimination, I found out that the culprit of the issue was the BrowserAnimations module in my app.module.ts. By removing it from my imports it the problem went away. I'll look into creating a Plunker to demonstrate it.

Update: This is described in this Github issue.

Update 2017-12-13: This has now been fixed with this PR, fix(animations): properly recover and cleanup DOM when CD failures occur.