Minor Bug - Boulderback not spawning

Not a big deal as far as bugs go but noticeable enough to make a post.

As the title says, Boulderback did not spawn in the foothills in act 9, I cleared the zone to "0 Monsters remaining" to make sure I didn't just miss him.

Once I made a new instance of the zone he spawned that time.

Possible reasons he didn't spawn:

- There was a transportation mission in the zone

This just happened to me today. Can't find boulderback. I didn't have a transport mission in my zone though.