I'm working through the Tchortist quests and encountered the tremors after talking to Eidein. I checked the west wing without asking the physics lab, talked to Six, and looked all over the place. No faceless. And the quest is no longer listed. So I'm totally stuck. Anyone else encounter this problem?

West wing is the place to go to check out the strange tremors so you are on the right track with that, talking to six is something that can happen but ultimately the quest comes to an end when you encounter the faceless at the end of the left west wing path, If I recall correctly six's path is slightly off the main left path.

If you run into too much trouble there is an excellent wiki for underrail if you are not already aware of it and that should answer any and all of your problems and questions.

I'm not sure about posting links on gogs section but just look up underrail wiki and you should find it.