Quibbling about Quaffles

I think we're missing some important information about Quidditch.Particularly about the scoring ball, the Quaffle.

I've been thinking about this for some time. I've tried to pay special attention whenever I read a passage in one of the novels where J.K. explains the game or describes people playing it. There's something that I don't get.

We know that the Chasers carry the Quaffle, pass it back and forth between them, and attempt to score goals (worth 10 points each) with it when they get down to the other team's end, right? We also read descriptions of the action in the various matches and find that the Chasers quite often lose control of the Quaffle when they are harassed, hit or otherwise hindered by either players from the opposite team or one of the Bludgers. Still with me?

My question is this: why do they lose control of the Quaffle so often?

The descriptions of this particular ball do not suggest that it is very large, nor very heavy, nor that it vibrates or jerks around on its own or attempts to escape anyone who holds it. And, when it is presented in the films, the Quaffle appears to me to be no larger and no more active than your average softball.

So why do the Chasers drop it so often?

Think about North-American-style football. In that game, the players carry a decent-sized ball and get hit, hard, often by several powerful players, on each play. And quite often the players from the other team actively try to pry the football from the ballcarrier's control. And yet fumbles are quite rare.

In Rowling's descriptions of Quidditch matches, whether played by the Hogwarts students or world-class pros, the Chasers are constantly dropping the Quaffle, sometimes even when a player from the other team does nothing more than nudge them.

Why?

I personally think the Quaffle must have some kind of energy of its own. It reacts when the player carrying it comes into contact with a player from the other team or a Bludger, making itself very hard to hold. That would explain all the fumbles, I think.

Maybe J.K. simply forgot to tell us about this special feature of the scoring ball in the sport of Quidditch.