Correct me if I am wrong, but isn't the Sony DW-Q120A just a rebadged LITE-ON DVDRW SHW-160P6S? According to codeguys website it is: HERE
If that is true, couldn't you download the official firmware from LiteOn, HERE and then just crossflash your Sony to it? That may help the drive function better, and provide you with the latest firmware (09/04/2006 according to LiteOn).
Hopefully someone with greater knowledge about crossflashing, etc. will chime in as well, but I had a SONY DVD RW DRU-700A and I successfully crossflashed to the LITE-ON DVDRW SOHW-832S. Good Luck and keep us updated.