when dropping a stack of items from the inventory you must hover over the stack and press Command+whatever key is assigned to "drop selected item" in controls. The "drop" control defaults at Q. when you attempt this with it assigned to Q, it will quit your client, because on Mac "Cmnd+q" is the shortcut to quit a window, similar to Alt+F4. it would be good if the key was changed from Command to either Control of Option in stead, so that it didn't interfere with system controls.