First of all – game is looking really great, thank you for putting it on Steam.
Now, to the question at hand. I apologies, if this question already has been answered, i used “Advanced Search”, honestly.
I am playing V19 Experimental Build 5 and got to a point, when xenonauts need to get their hands on Preator, as “Alien Leader Interrogation” entry stated. Unfortunately, these creatures are nowhere to be found. My forces landed plenty of battleships and carriers already, attacked three alien ground bases – no result. Maybe, I am doing something wrong?