Headset help: top cap bolt stuck in expander?

I was swapping out a new stem and have run into an issue with the headset. I know nothing very little about headsets so apologies in advance for any incorrect terms..

I think I may have overtightened the bolt when putting the top cap back on, it didn't feel right so I unscrewed to remove it and it came attached to (what I think is) the expander plug? I can't unscrew it all but can see the end of the bolt coming out.

Any suggestions? It's an integrated Campagnolo Chorus Hiddenset 1 1/8"

Here's what the steerer looks like

Yeah, looks the metal on metal interface needs greasing, and the compression bolt needs to come out of the expander bolt, you're right there, just hold the non threaded but with some pliers. If the bung won't come out, it might need a gentle tap to free it, put carbon paste on the face that touches the carbon when you put it back in.

Looks like the top cap is pinched between the bolt and the bit of the bung?

When you reassemble, check the bung is right down into the steerer (often they aren’t tightened up enough and then when you try and preload the headset it just pulls the bung out the steerer a bit) and add a spacer if required.

Thanks both – managed to separate the top cap from the bit of the bung!

How far down should the bung be when I reinstall?

Never mind, wrong advice.

Depends on the bung.

Doesn’t look to me like that one has a lip that wants to be sat down on top of the steerer, I’d probably just go with flush with the top of the steerer.

Have reassembled and feels good – thanks for your help 👍

Good stuff.