Second time's a charm!

My 12-35 is going back - at wide settings at infinity the frame edges and not up to acceptable standard for this class of lens. This has been reported in a few reviews so it may be a 'character' of the lens but as it stands I'm not convinced as I've seen sample pictures not showing this. If it comes back with 'within manufacturers tolerances ' I 'll sell it on an try another and another until I get one I'm happy with. Everything else about this lens is very good and I'm not going to give up just because of sample variation.