I've run into similar problems with the tech requirements. I've captured and interrogated everything that comes in up to medium sized ships to the point that I can't interrogate any more. All the "free research topics" are used up. And the only items that give me any more of those random ones are the humanist files. Except I've exhausted the academy engineers too. I've yet to come across AND capture the top tier units with the exception of a guildmaster, but the 2nd one captured doesn't give me a research topic for his code, despite the fact that I've researched The Solar Governor and had the game TELL ME to do that.
Idea? I mentioned this in my own post on the tech topic, but I'd like to reiterate here since it's a possible solution: Some tech should possibly be unlockable thru sheer numbers.
I have taken apart about 150 different laser guns. Of varying types. If my Brainers can't figure out how they work and how to make them after breaking them down DOZENS of times, they're all fired. And maybe tier it? So it takes X for laser tech, and 2X for gauss (though this may be a simpler technology, though 2X still makes sense since they seem to be higher dmg), and since Plasma is final tier (?) make it take 10X or maybe even not possible thru simple disassembling them?