NEX-6 SELP 16-50 back focus issue

Hi everyone,

Starting yesterday I changed Canon DSLR system that I have been using for last 7 years for Sony's NEX-6 with 16-50 kit. Unfortunately I have an issue of back focus, very visible at 50mm f5.6 from close distance (from ~25cm i get about ~5-6mm shift).

The problem has been confirmed by the technical people from the store that I bought it in. Again unfortunately, they do not have a replacement right now, neither for the body or for the lens, but we could make a very interesting test in the store: the 16-50 on another body (NEX-5N) works perfect. The same about my NEX-6 with an 18-55 lens. So it means that each one separately is working fine, but somehow the combination of the two is not.

Do you have any explanation for this? Is there a chance that any NEX-6 will work the same wrong way with any 16-50? I will do this test once they receive new stock (to find a replacement body or lens or both) but I wonder what to do if the results will be the same with any combination of the two.

Any similar problems that you encountered or heard of?

Many thanks!