This might be less of a bug and more of a suggestion, but I've found Future Prototypes to be more trouble than they're worth. I created some and used them to build a ship class; that part worked great. However, even once I researched the tech the prototypes were based on, the prototypes were still classified as FP. This prevents you from researching them and then building the ship class. I ended up recreating the techs as non-prototype techs and then modifying the class to use those versions instead.