I've been playing for a while now, with a lvl 40 character, and have pretty much been delving into every single cave or dungeon I come across to see how they look. As a result, I've cleared quite a lot of slave dungeons and freed approximately 60 slaves. However, I can't for the life of me figure out how to get the dialogue option for "Twin Lamps." In vanilla Morrowind, it's supposed to come up as a topic after you've freed at least 21 slaves, if you free a slave and then talk to them afterwards. However, that's not possible here because they vanish as soon as you free them. Talking to other slaves you haven't yet freed does not work, and speaking directly to Ilmeni Dren and asking her about "Business" doesn't work without the passphrase.
On a somewhat related note, I've also noticed that at the Caldera Ebony Mines, the Caldera Slave Key does not allow you to free the slaves in the mine. (I've already stolen all 3 existing copies of the key.) Is this option locked out to prevent you from ruining the House Redoran quest to shut down the Caldera mine?