On OS X using a trackpad pinch gesture to zoom in / out breaks panning and zooming. When a drawing is opened or created, pan and zoom functions work as expected. As soon as you use a pinch gesture to zoom in/out all zooming and panning operations (toolbar buttons and scroll bars) begin producing erratic behavior. The drawing has to be closed and re-opened to restore proper operation. Other open drawing windows are not affected and work properly unless you pinch gesture zoom in their window.