Ok. Obviously you should be running a cleanup more regularly, but otherwise, that all seems fine.
Have you tried these? https://www.damiensymonds.net/2015/09/black-boxes-and-other-weird-behaviour.html
Have you read this before?
Did the printer ask for CMYK?
Was the first print run CMYK as well?
NOOOOOOOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
https://www.damiensymonds.net/2010/05/making-pdfs-from-photoshop.html
Ok, in that case, I think we can get away with the easiest option.
Duplicate the Background layer
Go to the Canvas Size dialog, and extend the size at that side
Flip the new layer horizontally, then move it across so it lines up perfectly (zoom in greater than 100% view to ensure this)
Add a new blank layer and clone out as much elbow as needed
Hi Diana, yes, there are a few ways to approach it.
Do you intend to do anything else to the background? Change its colour in any way, I mean? Presently it's slightly shaded white (ie very light grey) - will that be how it remains?