Have had this happen a lot the last few days or so. No clue why. I did /bug it, but thought I should post it too because I suck at describing it. This was MQ, but it has happened with other NPCs too. Example: The bounty guy to start doing them.
I noticed this last night when doing the Main Quest. I just thought it was lag on my end. Guess I should be bugging everything and driving the devs wild.