Nec 3500AG 2.TG speed problem!

Hello guys
need your help here
I own a Nec 3500AG burner with F/W 2.TG and I use Vebratim MCC03 x16 discs.
I cant manage to burn at x16 speed I usually burn at x8 and rarely at x12.
When I tried to burn at x16 it failed and when looking on the back side of the disc I saw that it started burning after a while a gap of empty “ring” and then more burned info and nothing after because it failed. This error happened prior to firmware update.

How can I fix this problem so I can burn at x16?

The previous thread was already merged with the 2.TG support thread