I have Platinum Dual-layers with media code CMC MAG04 which my old and trusty 1635S writes to near perfection (no failed writes, nearly no bad discs after full write) but my spanking new LH-18A1P has managed do produce failures and non readable discs.
The drive came with GL03:
one occasion at about 2/3rd of the disc there are 2 ring of about 1mm not written at about 5mm from each other.
And other discs are just unreadable after 100% write
I flashed it with GL0C today, but that made things even worse:
Drive just kept on writing the lead in (% was after 8mins still at 0), theres a ring of ~4mm with very irregular writing.