I see no indication that you checked any of the items I mentioned, or for a reversed chainring (not reallyy a stab in the dark). Again, the cause must be something affected by increased chain tension while shifting. Please check the derailleur pivots and inner surface of the cage. Thanks.
p. s. You have an option that many do not - substituton. You can swap out another derailleur to confirm whether it is a factor. Also make sure the derailleur height and rotation is correct, as it's common to assume it's OK. As we have neither a side nor rear view of the derailleur it's my not possible to tell at this point.
Last edited by cny-bikeman; 03-04-14 at 06:53 AM.