I'm not sure if this has been mentioned before but... I know everyone's been complaing about sometimes the commander will upgrade a Turret Factory, and it won't let them place sieges. From playing in many many games, It seems there is a bug that resets it's "Yes, I've been built flag" So simply once the turret factory has been upgraded, and you can't place any siege turrets, just tell your marines to try to rebuild the turret factory by pressing the use key. It's worked every time the siege turret upgrade won't let me build sieges. As soon as they finish building it the second time Then you can place siege turrets. This is just an observation I made a few weeks ago, and I'm now starting to post here. Sorry if this has been mentioned before, just trying to help the community.