I have this problem too. And it's not only the charger - headphones are driving me crazy also. I've noticed that K750i and other "older" series have a significantly better connector than K610 and similar.

When I take a deep look, I see like my connector on my phone (k610i) is a bit curved... You know what I mean.

BTW, that's the only thing I don't like about K610 :D