Using virtualscroll leads to incorrectly applied css

Trying to get alternating row colors - I find that using the more performant virtualscroll leads to inconsistent results - even rows are not colored correctly once I swipe really fast up or down.
Reverting to an *ngFor - makes the problem go away. Bug ? Is this due to UI element reuse ?

On Ionic 2.1.18 - v2 app (typescript ang2) - Android device

// css
page-trans ion-item:nth-child(even){
  background: beige

// html - works
  <ion-item *ngFor="let entry of entries">

// html - doesn't
<ion-list [virtualScroll]="entries">
  <ion-item *virtualItem="let entry">