You can add -R Prodisc S03 to the list of discs burned on the NEC 3500 that do this.
When burned with 3500 firmware "Version 2 Milestone Release - Extreme" firmware http://freeweb.siol.net/tvajng/Quikee_FW.html, the BenQ 1620 cannot read the Mid code - at least with 1620 firmware B7T9. The transfer rate goes to 16X, and it kicks out an invalid sense information error when it tries to read past the end of the disc. The transfer rate is good (until the error at the end).
It happens every time for all Prodisc S03 discs burned on the NEC 3500 and scanned on the BenQ 1620. I overspeed burned these discs at 12X - I did not do any testing at lower burn speeds.
DVD Identifier reports "unsupported medium detected" and does NOT report the media type or name at all.
The discs all read fine in the NEC 3500 and they all read fine in a LiteOn 451. The discs also work in all the set top players I've tried them in, and the quality scans look good.
This looks like a firmware glitch in the 1620 that's being triggered by a NEC writing quirk.