You have some original post with INLINE attachment as [_ATTACH]#[_/ATTACH] there.
You QUOTE that post.
After that in your post you will that attachment from original post as an URL "Attachment 4".
When you click on that URL "Attachment 4" a new window is opened in browser with original image.
My suggestion is to replace that first click on URL "Attachment 4" with Lightbox popup as we now have when we click on "Attached Thumbnails" in original post.
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