If caching and oplocks are on and the redirector fails it can happen, same as the desciption of the SMB2 fix that is currently being tested.
In a nutshell the local cache has'nt been updated with what has happened on the disk, you will get a duplicate.

>I have never seend this happen before, but it appears that one of my tables where I use an AutoInc field (that I use as a primary key), has given me a duplicate value to 2 records.
>
>Is this possible?