Thanks for your quick answer!
This site seems to be the obvious place to look for updates but unfortunately my drive's not compatible with the firmwares provided on this website. They provide firmware for drives starting with "XJ-HD" and mine's calles "JLMS DVD-ROM LTD-166S".
EDIT: I figured it out! My drive was shipped with OEM firmware. After fixing the flash utility, I now have the original "XJ-HD" firmware and everything works great!