Blank area when scroll fast

I’m using ionic2 for iOS. There seems to be a strange block when scrolling.

When scroll to the top, the gray area as shown above appears (I have no such gray block defined in my code), while the expected content, as shown below, appears a few seconds later.

Although I do enjoy developing with ionic, I have to say, the scrolling experience is not so good, even on iOS. It’s slower than expected, and more importantly, the content appears too slow. I wonder if this is because I used it the wrong way. Here’s the basic structure of my code.

<ion-content class="page1">

    <ion-item-divider light>...</ion-item-divider>
    <ion-item *ngFor="#activity of activities; #i = index" (click)="startRecord(i)" class="item record-item">

Another problem is that, click event is not always triggered when click on ion-item on iOS, at the probability of 50%, while it works well with ionic serve on PC. And it works well on iOS for <button> item. Any idea?

If you can reproduce this issue in a plunkr or have an easy steps to reproduce, I think you should submit an issue in the github repository.

I found the reason after some attempts…
It turns out to be an element with z-index of -10. Not quite sure if this is a bug.