This is a wipe transition between an image without grading and the same image graded. Ungraded image is on the top half the graded image is on the bottom half. You will see the aspect ratio has been changed though i have not changed that and nothing in the grade or inspector suggests this. This seems to happen with a lot of the photos i grade. Is it possible when I zoom in to the image to look at the grade more closely using the scroller on the mouse, that this is changing the final output? Totally confounded by this.
You can adjust all sorts of sizing parameters on the Color page. This might be where you have accidentally changed aspect by changing the width. Have a look at your various sizing options. If width or height is not 1 then reset to 1 and it should be correct. If you trim sizing and copy grades it can send the wrong setting to multiple clips.
The sizing panel is on the lower right on the grade page (I use two monitors)
I would go through and turn off individual nodes to see if there is anything happening within nodes that might affect sizing or aspect. You can do node based sizing. I have not seen this behaviour. Are you using third party plugins? Or round tripping via Fusion for any reason? I’ve seen aspect issues in Fusion if you don’t start with a background in the right aspect ratio and then merge the still over that background to set correct aspect.