Horizontal blackline on image but not on print

I am having issues when scanning multiple A4 pages through the document feeder of my printer. The first page scans fine but the second and subsequent pages have a horiztonal black line approx 2/3rds of the way down the scanned page. I have tried scanning plain paper and the same thing happens. First page come out totally white but second, third, fourth and fifth pages come out with this horiztonal black line 2/3rds of the way down the page. It is not the printer-happens on different printers and it is not on the printed page. It only appears on scans when scrolling through the document with Adobe Acrobat Reader on the screen.

Could it be that Adobe thinks the page is shorter than it really is? I tried updating and the message was that there were no new updates available. Because the problem is only on the screen and not on hard copy it is something of an academic problem but it is annoying and was concerning until I realised the line didn't print out on the page.