Теряется фокус кнопки

При наведении на кнопку теряется фокус при положении курсора в пустом месте между границей кнопки и надписью кнопки.

Подсветка при наведении (зелёным цветом)

Здесь курсор между + и границей кнопки:

<Button x:Name="button_asave_plus" Content="+" HorizontalAlignment="Left" Margin="262,0,0,0" VerticalAlignment="Top" Width="20" 
    Style="{DynamicResource ButtonStyle}"/>

Стиль:

<Style x:Key="ButtonStyle" TargetType="{x:Type Button}">
        <!--<Setter Property="Background" Value="#444444" />-->
        <Setter Property="SnapsToDevicePixels" Value="true"/>
        <Setter Property="OverridesDefaultStyle" Value="true"/>
        <Setter Property="Foreground" Value="#FFFFFF" />
        <!--<Setter Property="Button.Background" Value="#00FF00" />-->
        <Setter Property="Background" Value="#00FF00" />
        <Setter Property="BorderBrush" Value="#555555"/>
        <Setter Property="BorderThickness" Value="1,1,1,1"/>
        <!--<Setter Property="FocusVisualStyle" Value="{StaticResource ButtonFocusVisual}"/>-->
        <!--<Setter Property="MinHeight" Value="23"/>
            <Setter Property="MinWidth" Value="75"/>-->
        <Setter Property="Template" >
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Button}">
                    <Border
          x:Name="Border"
          CornerRadius="0"
          BorderThickness="1"
          >
                        <ContentPresenter
            Margin="2"
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            RecognizesAccessKey="True"
                            />

                    </Border>

                    <ControlTemplate.Triggers>

                        <Trigger Property="IsKeyboardFocused" Value="true">
                            <Setter TargetName="Border" Property="BorderBrush" Value="#555555" />
                            <Setter Property="Foreground" Value="#90EE90" />
                        </Trigger>
                        <Trigger Property="IsKeyboardFocused" Value="false">
                            <Setter TargetName="Border" Property="BorderBrush" Value="#555555" />
                            <Setter Property="Foreground" Value="#CCCCCC" />
                        </Trigger>
                        <Trigger Property="IsDefaulted" Value="true">
                            <Setter TargetName="Border" Property="BorderBrush" Value="#555555" />
                            <Setter Property="Foreground" Value="#CCCCCC" />
                        </Trigger>
                        <!--Цвет при наведении мыши -->
                        <Trigger Property="IsMouseOver" Value="true">
                            <!--<Setter TargetName="Button.Static.Background"  Property="Background" Value="#000F00" />-->
                            <Setter TargetName="Border" Property="BorderBrush" Value="#90EE90" />
                            <Setter Property="Foreground" Value="#90EE90" />
                            <!--<Setter Property="BorderThickness" Value="1,1,1,1"/>-->
                        </Trigger>
                        <!--Цвет при нажатии мыши-->
                        <!--<Trigger Property="IsPressed" Value="true">
                                -->
                        <!--<Setter Property="Background" Value="#000000" />-->
                        <!--
                                <Setter TargetName="Border" Property="BorderBrush" Value="#90EE90" />
                                <Setter Property="Foreground" Value="#90EE90" />
                            </Trigger>-->
                        <!--<Trigger Property="IsEnabled" Value="false">
                                <Setter TargetName="Border" Property="BorderBrush" Value="#555555" />
                            </Trigger>-->
                        <!--<Trigger Property="IsEnabled" Value="false">
                                <Setter TargetName="Border" Property="BorderBrush" Value="#555555" />
                                <Setter Property="Foreground" Value="#90EE90" />
                            </Trigger>-->
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>