Edward,
if you swap the bulkheads and the high side moves then the bulkhead is a problem. if you swap the arms and the high side does not move then the arms are directional.

fyi, the parts i just received from stormers and are definitely symmetric. the ones you describe sound one sided. i suppose i got old stock from stormer's, but you might just try a new set of arms. maybe the 'dot'ed arms are the first generation?