When completing a quest in multiplayer the success dialog does not display, the target item is not taken, and the reward is not given. As a side effect, the town progress is not updated to open new items.
I know that there are a bunch of other glitches related to multiplayer but I think this one is a higher priority. Although there's a hurdle to solve (making sure that at least one of the players has the target object and somehow divvying up the reward proportionally) I plan on putting in a fix for this over the weekend but there's a bigger issue that should be discussed.
Can we make a new installer for the official version once this bug is fixed? There's a couple major features waiting to be released. The lighting compiler for sure and a few other I'm forgetting.