I cleared AQ40 on my druid and ported out (with the Dreamwalking Skill from Legion). I went from there through the Feralas portal (or to OG > portal to Uldum) and flew back to AQ40 to turn in the quests.
But it’s impossible to enter the instance again because there seems to be an invisible wall before the instance portal of both instances.
It seems there is some timewalking or phasing bug going on.