It turned out that there was something going on with the threads in the core, and also the bolt was slightly too big. Fortunately, we have several lovely people around who are mechanically inclined and (this is key) have the appropriate tools for all the things.
So there are new rollers on the press.
(Look at how shiny the new cores are! I hit the rails with a scrub brush and some solvent, too, so they’re looking pretty good too. I need to think of something to do with the bed of the press. It’s not actually rusty anymore, but it has some problematic spots that are a result of rust that was on it when we got it.)
(Even better: we are supposed to be getting a rag service soon. You may have no idea how wonderful that is. Trust me, it’s fantastic.)