Square image in my images after importing

[#1]

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.

[#2]

Go into Photoshop Preferences and make sure 

Legacy Compositing is checked ON

and Maximize PSD and PSB File Compatibility is set to ALWAYS

[#3]

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):

https://feedback.photoshop.com/photoshop_family/topics/reproducible-bug-in-feathered-layer-masks-pho...

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[#4]

Iain started a topic in the official feedback forum, and Adobe employees are already engaged, so others should please continue the discussion there:

https://feedback.photoshop.com/photoshop_family/topics/rectangle-appears-on-images-after-editing-in-...

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