LongListSelector stopped scrolling and freezes

I have a control LongListSelector(in PivotItem) in a Windows Phone 8 application. I see strange behavior. Once upon a time, LLS stopped scrolling. Like a hang, I can't scroll it. But I can use AppBar, Pivot, Button Backetc. And even GroupHeader and JumpList. This happened by chance (so far I have not found patterns) and quite often. I used to use LLS often, but these problems never happened.

The following is a typical scenario where LLS may freeze.

• Go to the LLS page.
• Scrolling LLS.
• Click the LLS element and go to another page.
• Return to the page using LLS.
• LLS does not scroll.

This bag can occur in other ways.

Main characteristics:

• I do not bind a large collection to LLS (my collection is about 10 - 50 elements (in 5 groups)).
• When LLS does not freeze, it works very quickly and without jerking.
• LLS elements have ListBox(1 - 6 string elements).
• I am using a DataTemplateSelector ( as implemented here) .
• Profiling does not show poor responsiveness when freezing LLS.

My xaml:

 <phone:LongListSelector Name="LLSSimpleSearch"  VirtualizingStackPanel.VirtualizationMode="Recycling"
                         ItemsSource="{Binding ListGroup}"
                         toolkit:TiltEffect.IsTiltEnabled="True"
                         Margin="12,0,-12,0"                                                                   
                         IsGroupingEnabled="True" 
                         LayoutMode="List"
                         HideEmptyGroups="False"      
                         GroupHeaderTemplate="{StaticResource LLSHeaderTemplate}"
                         JumpListStyle="{StaticResource LLSJumpList}"
                         ListFooterTemplate="{StaticResource LLSListFooter}">      

ItemTemplate

<questionary:QuestTemplateSelector Content="{Binding}">
<questionary:QuestTemplateSelector.Template1>
           <DataTemplate>
                <ListBox></ListBox> <!-- ListBox with small collect-->
           </DataTemplate>
<questionary:QuestTemplateSelector.Template1>

<questionary:QuestTemplateSelector.Template2>
           <DataTemplate>
           </DataTemplate>
</questionary:QuestTemplateSelector.Template2>

<questionary:QuestTemplateSelector.Template3>
           <DataTemplate>
           </DataTemplate>
</questionary:QuestTemplateSelector.Template3>

<questionary:QuestTemplateSelector.Template4>
           <DataTemplate>
           </DataTemplate>
</questionary:QuestTemplateSelector.Template4>
</questionary:QuestTemplateSelector>

In cs:

LLSSimpleSearch.DataContext = GYSearchViewModel.Instance;
GYSearchViewModel.Instance.Load();

ViewModel

private ObservableCollection<Group<Quest>> _listGroup = new ObservableCollection<Group<Quest>>();
public ObservableCollection<Group<Quest>> ListGroup
        {
            get
            {
                return _listGroup;
            }
            set
            {
                if (value != _listGroup)
                {
                    _listGroup = value;
                    NotifyPropertyChanged("ListGroup");
                }
            }
        }

public Load()
{
     MyDataSource.Load((r) => { ListGroup= r; })
}

Is there something strange here? Are there potential problems in this code? I am ready to give more comments if necessary. Thanks for the advice in advance.

UPDATE (problem solving)

I can't be 100% sure, but 99% is the problem ListBox.

<questionary:QuestTemplateSelector.Template1>
               <DataTemplate>
                    <ListBox ScrollViewer.VerticalScrollBarVisibility="Disabled"/>
               </DataTemplate>
<questionary:QuestTemplateSelector.Template1>

, ListBox LLS. , . , ListBox. IsHitTestVisible .

 <questionary:QuestTemplateSelector.Template1>
                   <DataTemplate>
                        <ListBox ScrollViewer.VerticalScrollBarVisibility="Disabled"
                                 IsHitTestVisible="false"/>
                   </DataTemplate>
    <questionary:QuestTemplateSelector.Template1>

.