Hi @FroggyC 
Then it’s probably because of their files settings, such as:
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max image width: Maximum thumbnail width of images in a post. Images with a larger width will be resized and lightboxed.
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max image height: Maximum thumbnail height of images in a post. Images with a larger height will be resized and lightboxed.
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min ratio to crop: Ratio used to crop tall images. Enter the result of width / height.
I may have read a bit too quickly.
Did the image appear correctly before the update?
If you right-click → Open image in new tab, does the image appear complete?
What settings have not their default value in settings → files?