Sooo..not sure if this counts as a bug but there is a set piece arrangement to raise your number of corner goals significantly (at least for my team). Basically set the two FB back, one DC to challenge keeper, the other to near post, the rest to lurk. Have your corner kicker aim at near post only and watch the goals come in. I think it has to be a bug since last season my DCs' contributed 20 goals to the team.