Can you exclude a bad drive? Even with the firmware this drive has now, it should work fine with Verbatim and Sony blanks. That said, I'd rather return the drive as defective than playing with firmware with questionable success.
Windows reports that drivers are up to date and I suspect the problem is firmware since the new drive has CH01 firmware.
I doubt, it is a firmware problem. Even the most crippled OEM firmware should be able to handle Verbatim and Sony discs.
You might try if cleaning the lens does help (no cleaning disc, try a soft brush at first).
I it possible and safe to try to upgrade the firmware using SFDNWIN.exe (and the TO03 BIN file) with the NOCHECK option?
It is possible, but I do not know if it is safe. Reason: These drives came in two flavours: "Master" and "Slave" configuration, which is determined by the firmware.
At first, you need to find out if your own drive is configured as master or as slave (the latter is not widespread, but such exists). Next problem would be to find out if that Toshiba OEM firmware is for Master or Slave type drives. I have no idea, that's why I vote for "not safe".
For Master type drives, I'd rather suggest to use Samsungs SCxx firmwares for this drive. For downloads, see my signature please.
What else might be causing the problem, and how can resolve it?
A dirty lens or a faulty drive. Each of these is more likely than a firmware related issue.
P.S.: Thread moved to Samsung DVD writers section.