It is actually pretty common on the clemente, I was told a few years back it was from the sheet being picked up and moved at printing.
I have owned more that had the issue than not, think I bought like 5 before I found one I was ok with. The pop shows a few PSA 8 but they dont come up for auction much.
My PSA 6 you can just see the mark but it didnt damage the card like many others but its still the reason this card got a 6 and not higher-
