Ngif inside ngFor with scroll

Hi there ,
I’m working on ionic 3 app and i’m facing a big problem , it’s about scroll
the scroll event isn’t fired when i use two custom components with ngif directive , both of them are inside ngFor directive
here is code : ( page-post-card & title-post-card ) are the custom components :
Tahnks


  <ion-list item-start *ngFor=" let post of notif_rec">

    <page-post-card *ngIf="post?.type_notif=='rec'" [post]="post" [isNotif]=true>
    </page-post-card>

    <title-post-card *ngIf="post?.type_notif=='levelup'" [post]="post"> </title-post-card>

  </ion-list>