can back focus be fixed?

I've got a 16-50mm too. Just new. Seems great so far. I have heard about all these quality control issues as well which has scared me a bit. One thing i can't get me head around is this back focusing issue with the lense. What is exactly going on and is it tested on various levels from manual to multipoint and centre focusing?

I too am a recent owner of the 16-50 and I have to say mine focusses perfectly. Just make sure any testing you do is under natural light, not the kitchen lamps in the evening !