What is the media code ? (you can have it using DVDIdentifier).
What about your current firmware version ?
For sure, your firmware version limits the writing speed on this particluar type of media to 4x. What you can do to overcome this limit :
- Find an updated firmware (more or less easy depending on your current firmware version)
- Use an unofficial fw version, assuming they implement increased writing speed with this mediacode (search this forum to find unofficial firmwares for your writer)
CAUTION : unofficial fw voids your warranty, use at your own risk (generally low risk, see the comments in the corresponding threads)
Edit : oops, s_reynisson answered while typing !