Checkbox loses its V on MouseUp (in grids only)

Hello again.

I have checkbox columns inside grids.

I'm using DataGridCheckBoxColumn and DataGridTemplateColumn, in order to place the
CheckBox style inside and fire events when Clicked.

The CheckBox won't click, or in other words - the V is checked as long as the Mouse is Down.

As soon as I pull the click up )MouseUp), if I'm inside the checkbox area, the V disappears.

I'm using style sheet for the CheckBox, can you see anything there that causes the
Checkbox to be unchecked when mouse up ?

It only happens in grids, when using checkboxes inside forms, they work fine !!!

HERE's the resource file for the CheckBox -

any help would be thanked !!!

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
                    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
                    mc:Ignorable="d"><ResourceDictionary.MergedDictionaries><ResourceDictionary Source="Shared.xaml" /></ResourceDictionary.MergedDictionaries><!-- Focus Visual --><Style x:Key="CheckBoxFocusVisual"><Setter Property="Control.Template"><Setter.Value><ControlTemplate><Border><Rectangle Margin="15,0,0,0"
                       StrokeThickness="1"
                       Stroke="#60000000"
                       StrokeDashArray="1 2" /></Border></ControlTemplate></Setter.Value></Setter></Style><!-- SimpleStyles: CheckBox --><Style x:Key="{x:Type CheckBox}"
         TargetType="{x:Type CheckBox}"><Setter Property="SnapsToDevicePixels"
            Value="true" /><Setter Property="OverridesDefaultStyle"
            Value="true" /><Setter Property="FocusVisualStyle"
            Value="{DynamicResource CheckBoxFocusVisual}" /><Setter Property="Template"><Setter.Value><ControlTemplate TargetType="{x:Type CheckBox}"><BulletDecorator Background="Transparent"><BulletDecorator.Bullet><Border x:Name="Border"
                      Width="30"
                      Height="30"
                      CornerRadius="0"
                      BorderThickness="1"><Border.BorderBrush><LinearGradientBrush StartPoint="0,0"
                                       EndPoint="0,1"><LinearGradientBrush.GradientStops><GradientStopCollection><GradientStop Color="{DynamicResource BorderLightColor}"
                                      Offset="0.0" /><GradientStop Color="{DynamicResource BorderDarkColor}"
                                      Offset="1.0" /></GradientStopCollection></LinearGradientBrush.GradientStops></LinearGradientBrush></Border.BorderBrush><Border.Background><LinearGradientBrush StartPoint="0,0"
                                       EndPoint="0,1"><LinearGradientBrush.GradientStops><GradientStopCollection><GradientStop Color="{DynamicResource ControlLightColor}" /><GradientStop Color="{DynamicResource ControlMediumColor}"
                                      Offset="1.0" /></GradientStopCollection></LinearGradientBrush.GradientStops></LinearGradientBrush></Border.Background><Grid><Path Visibility="Collapsed"
                        Width="10"
                        Height="10"
                        x:Name="CheckMark"
                        SnapsToDevicePixels="False"
                        StrokeThickness="2"
                        Data="M 10 5 L 5 10 M 5 10 L 0 0"><!--Data="M 0 0 L 7 7 M 0 7 L 7 0"--><!--"M 0 5 L 5 0 M 5 0 L 10 10"--><Path.Stroke><SolidColorBrush Color="{DynamicResource ControlDarkColor}" /><!--GlyphColor--></Path.Stroke></Path><Path Visibility="Collapsed"
                        Width="10"
                        Height="10"
                        x:Name="InderminateMark"
                        SnapsToDevicePixels="False"
                        StrokeThickness="2"><!--Data="M 0 7 L 7 0"--><Path.Stroke><SolidColorBrush Color="{DynamicResource GlyphColor}" /></Path.Stroke></Path></Grid></Border></BulletDecorator.Bullet><VisualStateManager.VisualStateGroups><VisualStateGroup x:Name="CommonStates"><VisualState x:Name="Normal" /><VisualState x:Name="MouseOver"><Storyboard><ColorAnimationUsingKeyFrames Storyboard.TargetName="Border"
                                                  Storyboard.TargetProperty="(Panel.Background).
                        (GradientBrush.GradientStops)[1].(GradientStop.Color)"><EasingColorKeyFrame KeyTime="0"
                                           Value="{StaticResource ControlMouseOverColor}" /></ColorAnimationUsingKeyFrames></Storyboard></VisualState><VisualState x:Name="Pressed"><Storyboard><ColorAnimationUsingKeyFrames Storyboard.TargetName="Border"
                                                  Storyboard.TargetProperty="(Panel.Background).
                        (GradientBrush.GradientStops)[1].(GradientStop.Color)"><EasingColorKeyFrame KeyTime="0"
                                           Value="{StaticResource ControlPressedColor}" /></ColorAnimationUsingKeyFrames><ColorAnimationUsingKeyFrames Storyboard.TargetName="Border"
                                                  Storyboard.TargetProperty="(Border.BorderBrush).
                        (GradientBrush.GradientStops)[0].(GradientStop.Color)"><EasingColorKeyFrame KeyTime="0"
                                           Value="{StaticResource PressedBorderDarkColor}" /></ColorAnimationUsingKeyFrames><ColorAnimationUsingKeyFrames Storyboard.TargetName="Border"
                                                  Storyboard.TargetProperty="(Border.BorderBrush).
                        (GradientBrush.GradientStops)[1].(GradientStop.Color)"><EasingColorKeyFrame KeyTime="0"
                                           Value="{StaticResource PressedBorderLightColor}" /></ColorAnimationUsingKeyFrames></Storyboard></VisualState><VisualState x:Name="Disabled" /></VisualStateGroup><VisualStateGroup x:Name="CheckStates"><VisualState x:Name="Checked"><Storyboard><ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)"
                                                   Storyboard.TargetName="CheckMark"><DiscreteObjectKeyFrame KeyTime="0"
                                              Value="{x:Static Visibility.Visible}" /></ObjectAnimationUsingKeyFrames></Storyboard></VisualState><VisualState x:Name="Unchecked" /><VisualState x:Name="Indeterminate" />                  <!-- <VisualState x:Name="Indeterminate"><Storyboard><ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)"
                                                   Storyboard.TargetName="InderminateMark"><DiscreteObjectKeyFrame KeyTime="0"
                                              Value="{x:Static Visibility.Visible}" /></ObjectAnimationUsingKeyFrames></Storyboard></VisualState>
                  --></VisualStateGroup></VisualStateManager.VisualStateGroups><ContentPresenter Margin="4,0,0,0"
                              VerticalAlignment="Center"
                              HorizontalAlignment="Left"
                              RecognizesAccessKey="True" /></BulletDecorator><ControlTemplate.Triggers><Trigger Property="IsEnabled" Value="False"><Setter Property="Background" Value="{DynamicResource TransparentBrush}"/><Setter Property="BorderBrush" Value="{DynamicResource TransparentBrush}"/></Trigger></ControlTemplate.Triggers></ControlTemplate></Setter.Value></Setter></Style><SolidColorBrush x:Key="TransparentBrush" Color="#00000000" /></ResourceDictionary>