I don't know why you get bad results, but i also think something is not right with the training!! I have all my players on medium, and one player is getting bad training 3 days in a row(he has PR 5), but ok maybe it happens. Also few players get training in other skills, different from what i set them to training! I mean how can player with training Tactical(teamwork, decisions) 3 days in a row to get training Determination, Pace, Agility??