The Case of the Disappearing Quest Module
 

This may very well be unrelated to Carbonite
On 2 different Demon Hunters, when I leave the Class Hall using the Horn/ Portal outside of the Fel Hammer & arrive on the edge of the Flight Deck in Dalaran My Carbonite Quest Module has disappeared from my list of installed addons inside the game & is also missing from Interface>Addons>Carbonite ( >Quests is no longer there) sometimes reload works & sometimes I have to exit the game completely & come back in, before the Quest Module reappears & it functions fine when it shows back up.
There is no error message that I can find & the only other thing that happens is the Class Hall Button disappears as well & returns at the same time.