I have to disagree, I believe it is a bitting issue. Why do riders choose a certain bit or pieced of tack? Because the right piece of equipment, combined with the right aids is the key to a happy horse and a good ride.
My mare is very responsive to my leg, seat and hands. I wouldn't say she is "leaning" on my hands, but she has a tendency to get heavy in the kk loose ring. I can definitely get the ride I want in a plain snaffle, but I figure if I can find a bit that she is a bit more responsive to, it would be a great situation for both of us.
She is a big mare (and a big moving mare!) and going with a light forehand and working off her haunches isn't her natural process. It's always an ongoing process ... :)
"No hour of life is wasted that is spent in the saddle."
"A horse is worth more than riches."