Yamaha CD-RW is the very best you can buy for PS2 purposes. So there will be an explanation lying in the info you didn't provide:

1 Yamaha Model and connexion method
2 Exact CloneCD settings
3 The game you were copying
4 Was it an original and if so/not did the source game work on the PS2
5 What is the modchip

No diagnosis can be performed without the above info.