ux:Property Binding fires once

Might be an issue with using Set but I am only able to display the modal overlay once


    <ModalOverlay ux:Name="ModalOverlay"  DisplayModal="false" />

        <Button Text="Show Modal">
                <Set ModalOverlay.DisplayModal="true" />


<Panel ux:Class="ModalOverlay" ThemeBackgroundColor="White" ThemeTextColor="Black" CanClose="true" >
<bool ux:Property="DisplayModal" />
<bool ux:Property="CanClose" />
<float4 ux:Property="ThemeBackgroundColor" />
<float4 ux:Property="ThemeTextColor" />

<WhileTrue Value="{Property DisplayModal}">
    <AlternateRoot ParentNode="{Resource FullWindow}">
        <Panel Color="{Property ThemeBackgroundColor}" Opacity="0.95" Visibility="Visible" >
            <WhileTrue Value="{Property CanClose}">
                <Text Color="{Property ThemeTextColor}" Alignment="TopRight"
                        Margin="4" FontSize="24" Font="FontAwesome" Value="&#xf00d;" >
                        <Change this.DisplayModal="false" />
            <Panel Margin="8">
            <!-- Content -->
                <Text TextWrapping="Wrap" Value="Lorem ipsum dolor sit amet, deleniti menandri...." />

This maybe related to the following line where I use the top right (x) to close the modal

<Change this.DisplayModal="false" />

This displays the first time, after dismissing, clicking on the Button to open the modal again does not show anything.