Why is it so hard to set a ball-screen in team play?

[wEEman33]

If you hold down the left trigger and ask the computer to set a ball-screen for you, you get pretty much a perfect screen every time.

However, if you try to set screens manually for your teammates, it seems like the game has serious problems putting your player in the proper position to make a pick.

When you hold down the left trigger to set your pick, it seems like you always end up facing the wrong way, and the pick becomes useless.

Is there some trick to setting good manual picks, or is this feature just broken when it's not being done automatically with computer players?

I ask because I was trying to get a pick and roll game going with one of my friends last night and we literally couldn't do it because his player just could not set a proper pick no matter how many times he tried.