For instance, Leipzig is constructing the Great Lighthouse. After using the SGE, I lose some techs (always bronzeworking, for some reason, the others are randomized losses) and then my production is cancelled. The advisor pops up and says "because we can no longer work on Great Lighthouse, production has been changed to Colossus" or something similar. This could be due to tech changes, I suppose? An AI civ lost their Pyramids and and another lost their Oracle in a similar situation in this same game.