the adventure can be completed, but the completion is not logged, ie when the popup appears to show ur (and your frens') completion timing. no chests are rewarded either.
tried for wings of gold and the fireflies collection in vb. another player who completed at the same time as i mentioned that he couldn't get the reward for wings of gold as well as for some other adventures, while some others did give rewards - he did not elaborate on which.
update: ~40 min after this post, the chests came, so the server was probably lagging. should be resolved now.