Maybe there is a link back to the live site but it does not cause the problem. I have another live site using GP theme with different plugins and settings and there is the same CLS issue.
On the staging site, I switched to another theme and the problem is gone. So I think you should accept that this CLS issue is related to the GP theme and had better look closely to solve the issue.
By the way, your screenshot makes my site public. I would be happy if you could remove that screenshot.
