Defenders stopped heading the ball

Here's the story. I was testing a tactic recently, started a new game, saved and then played a whole season. Attacking corners were set to Near Post and my defender (and others when played on that position) scored loads of goals simply by attacking the near post and heading the ball into the net . That was not what I was testing, though, but it was pretty obvious that every corner was half a goal.

Then I repeated the same season, same tactic, same players, same attributes, same opponents. This time I couldn't score even one goal after a corner! That very same defender (and I repeat, with the exact same attributes and morale more or less) just stopped trying to head the ball into the net. He always got into the right position but never attempted a heading. Most of the time he was trying to stop the ball with his chest and then shot, which usually failed miserably. :confused:

I tried with some other players who used to score after corners following the same pattern, but the same thing occurred. Am I missing something in the game engine or this game is just a pile of hot steaming random?

did your corner taker change?

No, it was the same guy both times.