Someone was copying information from one document into another Word document. The paragraph in the document to be added had shading round it, which was causing problems when copied over as shading was not wanted in the new document.
When pasting into a new document, you should see a Paste Options symbol at the bottom right of the pasted paragraph. Click on this and a dropdown appears asking whether you want to match the destination formatting or keep the source formatting or keep text only. Select Match destination formatting. The shading will disappear as will any other odd formatting that may have been in the original document.