This is something similar to what I have said. You play the away match, and get a win or a what appear to be a good result. When you play the home match, despite that formations and tactics appeared to be the same, but judging by what is happening on the pitch, there seem to be a significant change. In some cases, the opponent seemed to score goals easily or for fun while you as the home team, where you are expected to play better than what you did in the previous leg, your team seem to concede goals easily and fail to score enough goals to qualify. This game is very strange, but the there are a lot of similarities and hence, trends in what is happening around. I suspect 'match fixing' or predetermined results in terms of who will qualify and who will disqualify. In some cases, you may clearly observe what the game engine wants to do and how it does it. As a manager, there seem to be little to nothing that can be done to change the course that the game has decided it will follow. If you managed to make your team score say 4 goals, the opponent will likely find a way to score 5 goals (or just enough goals to qualify). Some of those goals scored against you will appear as if the opponent had a very easy task of doing so; not much resistance from your defensive players or your GK. All this is set up and made to occur by the game engine.
And if ever what is suspected is actually the case, I think this is not acceptable. We, as serious users, should make some serious complaints.