In another thread TDGriff wrote:
I'll contact them, but I'm not sure I want to hear their answer... I'm sure it's no longer under warranty. The lens may be, who knows, 6 years old, but it's hardly been touched!
It doesn't bode well for my view of Sigma lenses--I take great care of my equipment, and it's hardly been used. I would expect something like this after medium use over time or heavy use. Not after I've used the lens just a few times.
The quoted reply was inadvertently created as a new thread so I've put it here and deleted that thread.