Black link on right of page in Composition Mode

I changed the background image for Composition Mode, but now get a black line down the right hand side of the page that I can’t seem to get rid of.

Anyone know how to fix this?

What does the full image look like?


Does the line disappear if you move the cursor to the bottom of the screen (to activate the view settings) and then slide the “paper fade” setting all the way to the right?