Try use your bench players more. System recognizes the number of matches played by main eleven, and even on top form/morale their performances will inevitably drop low if you keep using the same 11 over and over. Had this problem two seasons ago. Since then i rotate players and still do well. Altho there are times i should win 10-0 and turns out a 2-0 by FK or even pure luck. Still it's stupid anyways.