elementname contracting damaged controltemplate

i have listview organization items. organization uses tradition groupstyle (expander). i have check box enhance fall groups when. works glorious untill i click manually organisation header enhance fall group. after clicking sole organisation stops respond check box selection. looks contracting damaged after user manually clicks group.

please advise i am doing wrong.

thanks lot.

sincerely,
vlad.

<window xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation'
        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
    <window.resources>
        <xmldataprovider x:key="mydata" xpath="/info">
            <x:xdata>
                <info xmlns="">
                    <item name="item 1" category="cat1" />
                    <item name="item 2" category="cat1" />
                    <item name="item 3" category="cat2" />
                    <item name="item 4" category="cat2" />
                    <item name="item 5" category="cat2" />
                    <item name="item 6" category="cat3" />
                </info>
            </x:xdata>
        </xmldataprovider>

        <collectionviewsource x:key='src' source="{binding source={staticresource mydata}, xpath=item}">
            <collectionviewsource.groupdescriptions>
                <propertygroupdescription propertyname="@category" />
            </collectionviewsource.groupdescriptions>
        </collectionviewsource>

        <controltemplate x:key="listtemplate" targettype="listview">
            <listview borderthickness="0"
                      itemssource='{binding relativesource={relativesource templatedparent}, path=itemssource}'
                      displaymemberpath="{binding relativesource={relativesource templatedparent}, path=displaymemberpath}">
                <listview.groupstyle>
                    <groupstyle>
                        <groupstyle.containerstyle>
                            <style targettype="{x:type groupitem}">
                                <setter property="margin" value="0,0,0,5" />
                                <setter property="template">
                                    <setter.value>
                                        <controltemplate targettype="{x:type groupitem}">
                                            <expander isexpanded="{binding ischecked, elementname=chkexpandall, mode=oneway}">
                                                <expander.header>
                                                    <dockpanel>
                                                        <textblock fontweight="bold" text="{binding path=name}" margin="5,0,0,0" width="100" />
                                                        <textblock fontweight="bold" text="{binding path=itemcount}" />
                                                    </dockpanel>
                                                </expander.header>
                                                <expander.content>
                                                    <itemspresenter />
                                                </expander.content>
                                            </expander>
                                        </controltemplate>
                                    </setter.value>
                                </setter>
                            </style>
                        </groupstyle.containerstyle>
                    </groupstyle>
                </listview.groupstyle>
            </listview>
        </controltemplate>
    </window.resources>

    <stackpanel>
        <checkbox name="chkexpandall" ischecked="true" content="expand all" />
        <listview itemssource='{binding source={staticresource src}}' displaymemberpath="@name" borderthickness="1" template="{staticresource listtemplate}" />
    </stackpanel>

</window>