The most annoying bug I've found so far is in the upgrade screen. Whenever I upgrade a unit or just look at my units through the upgrade screen, literally every available unit is superimposed in the little screen where it's supposed to show a 3D model of your currently selected unit.
For example, I can see a ship sticking out under the plane, as well as some parts of a tank, and an infantryman's head, which makes it look like he's riding the plane. This happens regardless of Nationality or Affinity.