Not sure if this is a bug or not; it's happened to me several times. I save the game in battlescape and then immediately end my turn. A series of events happen on the alien's turn and then I immediately reload the game from the save point and end my turn again, but a different result happens than the initial time.
Now if I keep reloading, that saved game, the second event always happens, but it is different than what happened the first time before reloading. Why did the results change in the saved game?
As an example in a current game I have saved, an alien threw a grenade and killed one of my men. I reloaded the game because I wasn't paying attention talking to someone in the room and wanted to see where the grenade came from. Well upon reload, the grenade still got thrown, but my man didn't die. No matter how many times I reloaded, they kept living.
This is in the 1.0 version and the save scum option is turned off.