I used to find it hard to score from corners in the beginning, but I think I have figured it out now.
I used to concede a lot of goals from defensive corners and did not manage to score a single goal with my KAA Ghent team.
Now I always use "short" for attacking corners (have one of your best crossers set up to go for the short option).
Since then, opponent defenses seem to struggle. My team scores a lot more from corners and if we don't manage to score, we at least seem to be able to have a shot on goal from almost every corner.
It could be that my opponents will learn from their mistakes later in the game, but for now this looks like a glitch to be honest.
I find it a bit unrealistic that my average team always manages to outwit better defenses whit a simple short corner.
I stopped conceding goals out of defensive corners by setting the match prep to defensive set pieces for a couple of weeks.
Let me know if this works, hope this works for Spurs GlenYid ;-)