very light light line above the printed text of a four-colour offest catalogue

Hi all,

I received the product catalog from the printer.
I noticed that on a page with black text over a black screen there is an undesirable effect that is absent from the PDF file supplied to the printer.
it is a very light white thread
I have attached two images, the second is more evident.
waiting to ask the printer, what do you think?
a problem with the CTP?

thx