The EGR can stick after getting clogged with carbon. There are 3 valves that open and close. I've had success cleaning the valves by removing the EGR and using a toothbrush with a combination of brake fluid first, then seafoam. Spray the toothbrush, not the EGR. If that doesn't work then you will need to delete the EGR (if it will still pass emissions) or replace it.