If you are signed up for a zakum expedition, and DC (or CC), for any reason, you will not be warped into zakum when the expedition leader starts. I didn't see this on the current list of bugs, but this is really frustrating. Oftentimes the client itself will crash for any number of other reasons, and this leaves people SOL if there isn't a GM on.
I'm not sure if this is a bug, once you sign up for the expedition it counts towards your two runs in a 24 hour period. So if you d/c after signing up but before going into Zakum's Alter you're kinda screwed. Yeah it sucks, but I don't think it's actually a bug. I think that's just the way it counts your zakum attempts.
It's a bug, you're supposed to be warped in since you are a registered member of the expedition. Even when you return from your DC, Adobis still lists you as a registrant of that run, thus you should be warped in with the rest. I don't quite understand what you mean by "that's just the way it counts your zakum attempts". DCing and coming back doesn't use up another 1 run slot, since Adobis still lists you as a registrant of the run, just that he doesn't warp you in. If what you mean is that it's probably a script that prevents more than 2 warps per 24 hours, I doubt so because some of my mates who dc'd in their 1st run slot were still unable to be warped in after they dc'd.