When you have an Image inside the ListViewTemplateCell like this:

<telerikListView:ListViewTemplateCell>
    <telerikListView:ListViewTemplateCell.View>                         
                <Image Source="{Binding ImageSrc}" HorizontalOptions="Center" VerticalOptions="Start" />               
    </telerikListView:ListViewTemplateCell.View>
</telerikListView:ListViewTemplateCell>

in certain cases not all images are initially rendered.  As soon as you click any of the images, all of them are loaded.

As a workaround, avoid setting HorizontalOptions/VerticalOptions properties to the Image.