I've noticed guys fumble about 10% of the time if you use the highlight stick while being tackled. I've learned to just not use it. If you just let the guy just finish the tackle it should cut your fumbles way down.
Ok..again, if I'm playing CPU vs CPU I don't use any controls nor the highlight stick, nor anything. The QB fumbles on his own when he scrambles. I've already bug reported this. I was just curious how many other players this was affecting.