For the 3rd Adventurer's Assignment, the Obtain Monster Riding item seems to be bugged. I have already obtained a mount, but it still marks it as Incomplete.
Did you get your mount a long time ago (as in years)? If so, you might have gotten it before the current quest to get it was added, which is what Olaf is checking for. You'd need to drop and reobtain it for the completion.
