Okay, we had this problem ourself with a certain game once. The fix was simple.
Get 2 pieces of regular stick tape and tape them next to the hole in the center of the disk, on the label side. Per the poorly drawn diagram below.
The PS2 can then grip the disk better and re-read any specific data it needs to read easier. It sounds stupid but it worked with 2 of our disks on our PS2.