Only suggestion I have is drop the burn speed and see if that makes any difference.
I don't use RW disks as I found them far too unreliable. I could burn a disk, and check it and it was fine then try it again a while later and it wouldn't read properly. Sometimes it wouldn't burn and sometimes the disk just stopped working for no apparent reason.
I use the plain R disks now, create a multisession disk and just keep adding till its full.