I apologize for not looking at your screenshot. Unfortunately, this is not something that a screenshot helps much with. The line appears to be behind text since it is occluded by the shading in your table. While it might be a border, it would not be a paragraph border. It is almost certainly a graphical element and may be in the header-footer layer.

Try making a copy of your document and delete all other content. Then post it here using the Go Advanced Button at the bottom and then the paperclip icon to attach the copy.