I have also had similar problems. In a three way game my friends and I finished recently, two players managed to colonize the same planet. Both recieved income for the planet and were able to build structures in orbit. Whenever a player built a structure, it would show up on both player's screens as belonging to that player. For example, a planet was colonized by a TEC player and a Vasari player, and they both built Broadcast Centers/Media Hubs. On each player's screen, they each had a Broadcast Center and a Media Hub belonging to their planet. On a third player's screen, the planet belonged to the TEC player and only showed the Broadcast Center. We didn't get to investigate too much further as the game crashed about five to ten minutes after we noticed the bug.