I would definitley call Dillon and ask for the alignment set, they shipped it right out to me, saturday mornings at opening time is easy to get in, last time I called the lady told me it may be 15 minute wait! I laughed and said 15 minutes would be great!
The alignment pin fits in the powder drop die and fits into the primer seater hole (with the primer seater removed) if the platform is lined up.
Mine moves slightly in the bottom position and is very solid in the up position, the main difference between our presses is my platform is steel, yours is cast aluminum and may be slightly differant, I havent seen one up close, on my steel platform the only way I could see it being off is if it shifted on those screws or if it bent. Hope you find it and let us know what the final outcome was.