Upload & Sell: Off
I have had (2) decentered lenses, one of which was a 24-70 II and the other a 17-40... Sent to Canon and they attempted to fix it, but no help at all. I exchanged the lens for another which was perfect.
Both times thing, both lenses did not get fixed by Canon for whatever reason. I even sent examples and all that. The one improved slightly, but still bad. Exchanged that one too... Learned after that to not even try to get them repaired, just send them back and get another.
I had two de-centered lens, one was the 50 1.4 and the other 16-35. I sent them both to Irvine, both came back fixed and sharper than ever. In fact, both lens, wide open, are now sharper than most of the internet reviews that post the 100% crops for comparison.