I think you need to be more specific,
i'm not saying i can help but is it original or backup?
and has the system been fiddled with? ever been opened, is there a modchip present?
etc...
if its original and the system hasn't been messed with in any way, then it could just be laser wear. But don't take my word for it, i don't know much about how a PS2 works.
I've heard of people having lots of problems with DVD rips of this game, such as disk read errors for one. So if it is a DVD rip, i'd suggest just buying the game
It's well worth the money.