When programming a 4D SVG image for user interaction the object's response to Mouse Events can be controlled by using the "opacity" value of the "fill" attribute. An object with opacity of less that 10% will not respond to mouse events, therefore you won't get its ID value will when calling SVG Find element ID by coordinates in case of the On Clicked form event. Objects with a fill opacity of 10% or greater do have their user assigned ID returned by SVG Find element ID by coordinates when used in that fashion. See Responding to a User Click on an SVG Image for more information.