I've noticed some noise in the image on my 6 year old 27' LED Cinema Display (the model that predate the Thunderbolt display). It manifest as noise in that is only 1 pixel row across but goes down the screen some way and there can be several lines at a time. I have confirmed it happens on my custom gaming desktop, my HP laptop and my 2013 iMac. Before I go arranging an out of warranty repair with my local Authorised Repairer (no local Apple Stores) (assuming the parts for it are even still available) is it possible for any external factors to be causing this like power? I ask because my 2013 iMac has an image retention issue that doesn't happen when the Apple Authorised Repairer looks at it in their store. Thanks.