I made the same observation in level 7 (had there a loss/draw streak of 6 matches quite early in the season, which costed me the league title (and I did not make it out of the CL group stage). I did not know at that time the reason and got quite angry, because formations did not work.
But then I took players with bad marks out of the team, did some test matches, gave the players that way confidence and like dv8r also some transfers. It worked and the game ran from that time on "normally" (as far as one can say it), but it costed a lot of nervs.