Since buying and installing Leviathans, I've had a strange bug where by certain techs in certain tech trees don't go away once research, eventually ending in a dead end where I'm unable to research any more techs in the tree.
So, for example, let's take the Engineering tree. I train Engineering Facility, Tech 2 Spaceport, and Solar arrays. When the next three come up, the Engineering facility is there again but because it's already been researched, it can't be selected for research again, leaving me with two out of three to chose from. Then let's say I research Robotics, then Fusion Missiles, when the next three techs appear, two of the three are Engineering Facility and Robotics, leaving me with one. If I'm lucky the third teck will be something I can research. If I'm not, all three will be the Engineering Facility, Robotics and Fusion missiles leaving me with nothing left to research and the entire Engineering tree blocked off. It's usually a little further into the three before this happens, usually somewhere between early and mid-game. It's also not limited to Engineering, I've seen it occur in Physics, although not yet seen it occur in Society.
Steps I've taken are disabling all mods, disabling all DLC and even reinstalling the game. The latter works for a while but then comes back in after the first game. Point of note: When I uninstalled the game I deleted any and all folders associated with Stellaris, including the save games, yet it comes back eventually and means I can't complete a game.
So, for example, let's take the Engineering tree. I train Engineering Facility, Tech 2 Spaceport, and Solar arrays. When the next three come up, the Engineering facility is there again but because it's already been researched, it can't be selected for research again, leaving me with two out of three to chose from. Then let's say I research Robotics, then Fusion Missiles, when the next three techs appear, two of the three are Engineering Facility and Robotics, leaving me with one. If I'm lucky the third teck will be something I can research. If I'm not, all three will be the Engineering Facility, Robotics and Fusion missiles leaving me with nothing left to research and the entire Engineering tree blocked off. It's usually a little further into the three before this happens, usually somewhere between early and mid-game. It's also not limited to Engineering, I've seen it occur in Physics, although not yet seen it occur in Society.
Steps I've taken are disabling all mods, disabling all DLC and even reinstalling the game. The latter works for a while but then comes back in after the first game. Point of note: When I uninstalled the game I deleted any and all folders associated with Stellaris, including the save games, yet it comes back eventually and means I can't complete a game.