AF issues with select serial #s of Sigma OS lenses: 120-400, 150-500, new BIGMA

Sigma has issued an advisory notice that select BIGMA OS (50-500mm OS), 120-400mm OS and 150-500mm OS lenses may have autofocus issues. This appears to be a limited production issue as Sigma gives a range of serial numbers of potentially affected lenses. Check below for details on how to find out if your lens may be affected and how to have Sigma check it out for you.

Further Reading
+ Phototography Blog
+ dpreview
+ AP UK
+ Photoscala