MouseCallback e.Cancel not working in last version of Rhino 8

Rhino Developer
1

Hello everyone,
My implementation of MouseCallback use to work in previous versions of Rhino 8 but now it doesn’t cancel the original click when i use e.Cancel.

protected override void OnMouseDown(MouseCallbackEventArgs e)
{
    if (e.MouseButton == MouseButton.Left)
    { 
        e.Cancel = true; 
    }
}

Is this problem known already or am i missing something ?