There’s a bug during the Ballon Tower Tourist achievement.
The chest near Crossing Waypoint, in Queensdale, is unable to open. It appears like it’s already opened, but I’m sure I didn’t opened it, since it was just my 4th chest.
And I know some other players can’t open it as well :\
Hope you can fix this!
P.S. – (And I just discovered that there are more chests available than the ones you need to complete the achievement, so the bug is not that relevant I guess. But still, I’ll leave it here in case you might want to fix the chest ^^ )