demonstrate weird scrollbar in ionic 4 menu component while in RTL , using @ionic/angular: 4.0.0-dev.201901162054.ceae5d2

app.component.html

<ion-app>
  <ion-split-pane>
    <ion-menu>
      <ion-content>
        <ion-list *ngFor="let i of [0,1,2,3,4]">
          <ion-menu-toggle *ngFor="let i of [0,1,2,3,4]">
            <ion-item>
              <ion-label>
                Page #{{i}}
              </ion-label>
            </ion-item>
          </ion-menu-toggle>
        </ion-list>
      </ion-content>
    </ion-menu>
    <ion-router-outlet main></ion-router-outlet>
  </ion-split-pane>
</ion-app>