Major spoilers ahead!

During a Thieves Guild quest "Andothren Regained" after killing Vals Varano and using a recall spell to teleport back into the guild hall in Bthangthuv, quest does not progress. Killing all the Camonna Tong attackers does not progress it. 

Can be worked around if the quest stage is set to 175 (Bthuangthuv is under attack) prior to teleportation and after Verano's death.