Ever since the patch, it seems like you can't lead expeditions after one run. You have to re-make it after one run if you want to fight Zakum twice for example.
Before, you could change channels and lead an expedition yourself OR pass captain to someone else in the expedition and they could lead on the same channel that you did the previous run on.
Was this a new feature added? It's a pain in the ass to say the least. I've yet to check this problem with other boss expeds, but it's annoying at Zak.