DVR-218L slow speeds; unresponsive

I have 2 Pioneer DVR-218Ls in a Primera BravoPro Xi2. I’m using 16x Verbatim and Taiyo Yuden DVD-Rs. It’s taking 15-30 minutes to burn 4GB. It seems to start off going around 10x until about 1GB in, then it slows to 4-6x, maybe slower.

When it does this, the drive gets very loud (from the moment the burn starts, not after 1GB). If I attempt to abort, it seems unresponsive. The light is on, the drive is making noise. After awhile, it responds. But if I abort the job at say 10%, when it finally responds and I get the disc out… it seems to be completely burned.

I have gotten it to work OK a few times. When it works, the drive is nearly silent. I can abort it and it will almost immediately stop.

What is causing the drives to do this? Any ideas?

Probably its just the firmware on the drives in combination with the write strategies used.