Hi @flgallows ,
Try cleaning the scanner glass under the ADF.
Any speck of dirt or grime on the scanner glass will create a solid line as it is between the scanner sensor and the document being copied.
Here’s an image taken from p.34 of the [http://h10032.www1.hp.com/ctg/Manual/c04204791|user manual] showing how to access the scanner glass and where and how to clean under the ADF.
[image|1699172]
(click on image to enlarge for better viewing)