you got a dud!
Get over it!'
Every time that I think that I have, that it's but a distant bad dream, something comes along to hit me in the face with it again.
I have no idea if mine was a bad copy or not; all I know is that I know nobody, personally, whose work I admire, that uses zooms professionally. But then that's just me. Also, why would I go through all the crap of ordering another one only, perhaps, to find exactly the same problems? Mallorca isn't a place where you can keep buying new lenses, try them out, and return them with a smile if they suck. In my case, I ended up having to buy another lens altogether just to get the dealer to look at my situation and allow me to get rid of that zoom. Also, the physical size of that zoom makes it anything but pleasant to carry around. In a way, I'm glad that I had valid reasons for getting shot of it.
But I'll try to remember not to mention it again.