I'm currently doing the mage grandmaster quests, and in the first mission (the one where you fight NPCs) I occasionally get this weird event... the NPC I'll be fighting just poofs with black smoke, Lezaro says something about a fighter needing more spirit, and then nothing happens. I have to exit and restart the mission.
It's not time running out since it usually happens in the first 5 minutes or so and the time limit is 90...
It's not all bad since redoing it just gives me more EXP but it's still annoying.