I tried several different searches, so either I can't get the right search terms or it hasn't come up. In a quick battle with a human opponent we have a very battered city landscape. LOS is great in any straight line, so I put some anti-tank guns in large arty shell craters during setup. I checked all the LOS's from the guns, and everything was fine.
However, on my first turn after setup, the same guns, just where I placed them with fine LOS's, now have LOS's of 5-6 meters at most. Has this happened before? If so, is it a bug, or is there a gameplay explanation? I've never had an LOS change so dramatically from what showed at setup.