i had the same problem on four of my six rods and it was a real pain the butt to remove them. two of them popped with a little persuasion. one of them required vice grips above and below to twist the wedged washer free. the last i had to resort to a blow torch to expand the aluminum and break it free. when i reassembled, i slathered everything in lanacote, and i mean slathered, probably too much. i'm not sure i understand why they're alu, but i suppose it's to provide a little give in the system. a couple of mine were slightly misshapen.