Gamestop and Xenosaga Don't Mix

This post is a warning/story of my trouble with a copy of Xenosaga: Episode 1 I bought from Gamestop.  I was looking though the massive PS2 bins at Gamestop looking for a solid RPG; then I saw Xenosaga.  I was thinking in my head "with a name like Der Wille Zur Macht it has to be good.", so I gave the cashier a fiver, made my way home, and popped it in my PS2.  The game was great!  I played for seven hours straight loving every second of it.  Okay, now your thinking, "where does the not mix part come in."  To answer you question right now.  I walked into the elevator on the Elsa clicked "yes" to start her up... and it froze.  I sat there in silent fury because I hadn't saved in a while and Xenosaga has no auto save system.  It was just an unlucky one time thing right, NO!  I restarted the PS2 at least five times, and every time I got to the elevator it froze.  After my anger had subsided and I realized I only spent five dollars on the game I went to eBay and typed in Xenosaga: Episode 1 Der Wille Zur Macht .  I found a copy for only .99 cents and bought it.  Everything was going well with this copy of the game.  I made it all the way to the last boss and killed him without having anymore trouble.  After I beat the boss however, it went into a cut scene where it froze again.  I lost and hour and a half of game play and I had to beat the boss again.  Naturally I took the game out of the PS2 to inspect it, and what do you know it's my original copy of the game.  Some how the eBay copy got switched with the Gamestop copy.  It all works out in the end, but everything would have been good if I never bought that copy from Gamestop.  I guess the moral of the story is check every disc from Gamestop, or any use video game shop, before you pay for it.