Repairing Folding Wood Party/Wedding Chair (Brass Dowel)

I'm trying to fix a nice-ish but also sentimentally valuable, fairly well made wood folding party/wedding chair.

The main hinge is a pretty nice, strong 3/8" brass dowel (with PVC spacers).

But one of the ends (caps?) has fallen off.

So, while the chair is vertically strong, it's a little wobbly, and I'm trying to tighten it up.

One of the ends fell off and my dad fixed it, kind of, by filling the end with epoxy or fake wood, then drilled into that and set a screw. But that only kind of worked. But there's basically no load, so it did mostly work.

I'm trying to fix it better.

Is the end cap typically threaded? Pounded in?

I'm thinking it's pounded in, given there's no way to take it apart once it's put together. Only 1mm of clearance around the edges of the cap or whatever it is, so I can't pull with a pair of pliars

But, first, I need to understand how such a dowel assembly is put together.