MVVM - WPF Button using command delegation is giving inconsistent click behavior

I have a composite button control built up as a styled Button containing a StackPanel containing an Image and a TextBlock.  The issue I am having is that actually clicking the button at runtime is surprisingly difficult and giving inconsistent behaviors.  If I mouse over the button and the hover style takes effect (changes background color of button) the button is unclickable.  If I minimize my window and maximize then "sneak in from below" I can click the button as long as I haven't moused over far enough for the style to take hold. 

Here is my xaml:

<Button Command="{Binding ButtonClickedCommand}" CommandParameter="ManageCustomers" Style="{DynamicResource MyToolBarMenuButtonStyle}"><Button.ContextMenu><ContextMenu><MenuItem Header="New Customer" Command="{Binding ButtonClickedCommand}" CommandParameter="NewCustomer"/><MenuItem Header="Customer Notifications" Command="{Binding Path=CustomerNotificationsCommand}"/></ContextMenu></Button.ContextMenu><StackPanel Orientation="Horizontal"><Image Source="/OurProject.Resources;component/Graphics/ppl.ico"/><TextBlock Margin="3,0,0,0">Manage Customers</TextBlock></StackPanel></Button>

When I wire this up differently using click events in the code behind that delegate to an ICommand in the ViewModel, the style is applied consistently and there are no button anomolies such as I described above. 

What gives?

[edit]

inside the ViewModel(CanExecuteButtonClicked simply returns true):

public OurToolbarViewModel(IEventService eventService)
{
   EventService = eventService;
   ButtonClickedCommand = new DelegateCommand<object>(HandleButtonClicked, CanExecuteButtonClicked);
}
public ICommand ButtonClickedCommand { get; private set; }
private void HandleButtonClicked(object args)
{
    EventService.GetEvent<ViewChangeEvent>().Publish(args as string);
}
 

The Style's Template:

<Setter Property="Template"><Setter.Value><ControlTemplate TargetType="{x:Type Button}"><Border SnapsToDevicePixels="True" x:Name="Bd" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" ContextMenu="{TemplateBinding ContextMenu}" ><Grid Width="Auto" Height="Auto" x:Name="Grid"><Grid.ColumnDefinitions><ColumnDefinition Width="Auto"/><ColumnDefinition Width="Auto"/></Grid.ColumnDefinitions><Button Grid.Column="0"  Content="{TemplateBinding Content}" Style="{DynamicResource MyToolBarButtonStyle}" Background="{x:Null}" BorderBrush="{x:Null}" BorderThickness="0.7,0.7,0.7,0.7" Padding="3" /><Button x:Name="triangleButton" Grid.Column="1" BorderThickness="0.7,0,0,0" Style="{DynamicResource MyTriangleButtonStyle}" Background="#00DE2424" BorderBrush="{x:Null}" Padding="0,0,0,0" Click="triangleButton_Click" /></Grid></Border><ControlTemplate.Triggers><MultiTrigger><MultiTrigger.Conditions><Condition Property="IsMouseOver" Value="True"/><Condition Property="IsFocused" Value="False"/></MultiTrigger.Conditions><Setter Property="Background" TargetName="Bd" Value="{DynamicResource MyMouseOverOrangeGradientBrush3}"/><Setter Property="BorderBrush" TargetName="Bd" Value="{DynamicResource MyDarkOrangeSolidBrush}"/><Setter Property="BorderBrush" TargetName="triangleButton" Value="{DynamicResource MyDarkOrangeSolidBrush}"/></MultiTrigger><Trigger Property="IsEnabled" Value="false"><Setter Property="Foreground" Value="#ADADAD"/><Setter Property="Background" Value="{DynamicResource DisabledBackgroundBrush}" TargetName="triangleButton"/></Trigger></ControlTemplate.Triggers></ControlTemplate></Setter.Value></Setter>

The firing of "HandleButtonClicked" from the main body of the button is where my inconsistencies lie.  There is a context menu as part of this button control, and the eventing from the "New Customer" button is behaving perfectly as normal. It's as if the style is getting in the way of the click event when it is applied to the main body of the button.

Anyone have any ideas?