Blarg. The inner sleeve of the section in my TWSBI Vac 700 just broke. Ink poured out of the nib when that went down.
I just emailed Philip at TWSBI. I bet he sends me a replacement very soon. They're good about this sort of thing at TWSBI.
**Edit: Philip put a replacement in the mail today. Want good customer service? Buy a TWSBI.