The Azj-Kahet quest line for Rak-Ush Swarmery does not conclude correctly.
You can start the quest “…And Now I’m Arachnophobic” then complete the subsequent two quests after that without starting the quest “Spiders!”. If this is done out of sequence and even with all quests complete, that segment of the Azj-Kahet Sojourner cannot be completed.