There's one thing I never got in Star Wars. The first Death Star was destroyed because there was a small ventilation shaft that lead to the core of the station and which would let only a small projectile through. So why would the Imperials rebuild it with a bigger ventilation shaft to allow ships to fly into it? It makes no sense, did they not learn the first time round?
And why did they not have better shields? OK, they did have a shield but it had to be generated from down on a planet. If I had given the location of the base to rebels to get them to come into a trap I would at least build a shield generator so if the planet one failed, which they thought it might, I would have a back up. So why didn't they have a second shield generator?