Hmm, looks like you might need to do some more content. The counter for "TAUR_STADIUM_TOWEL" is only two, and it needs to be more than three to get the unlock scene. Don't forget you need to be backer as well. Good luck!
flags["AMBER_INTRO"] = 1 in console, or edit the save. It's a really old bug where the intro wasn't happening correctly. So the game doesn't think you "know" her name.
edit: I'll submit a fix for next patch.
In Bast's case and perhaps others, it was because their game is partially in a game over state: gameOverEvent is true. Could have been a bad undo or something, that feature is very incomplete.
Is the Uthra sap thing just an initial cap issue? Fixed that, wondering what more was going on.
Edit: I believe I was able to fix all the others just now for the next patch.
So Rivet and Aliss both have a little bit of code so they orgasm on a cycle even if you aren't around. I'm not sure why this is so for Alyiss, but it seems Rivet will change a bit over time when she goes without sex with you. So it is deliberate.