This is really just annoying especially later in the game and I want to see if anyone else has had this problem.  Before, when I would research upgrades for buildings, the now obsolete building would disappear and I would be left with the new one (ex. Traditional Factory disappears and now you can only build Xeno Factory).  Now whenever I play, the obsolete buildings no longer disappear, meaning that later in the game I have literally dozens of choices of buildings because nothing has disappeared.  I'm not sure if there was an option I hit that did this or what but its really frustrating so if anyone knows how to fix it that would be great.