Hi, I have a square outline in my images in Classic, this started happeing after the latest update, if I export the image it is fine but it is highly frustrating and annoying to have this in my images when I try to edit them, I don't know which is the true colour, the dark outside or the lighter inside.
I am using a new iMac on the latest Mac OSX.
You can see it in this image here where there is a lighter square area inside the image.
Note: This happens when I edit in photoshop and then return to Lightroom, so the files are PSD, TIFF or PSB.
Can't belive this wasn't found in testing, probably because of the lack of it.
Iain, reading through the jumbled order of replies, it's not clear that you've tried enabling the Photoshop option Preferences > Performance > Legacy Compositing, as suggested by Bob Somrak, and then resaving the image after making a trivial change. There is a bug in PS 21.0 and 21.1 that incorrectly renders the final image as seen by LR and other apps (PS displays the image correctly):