can you detail how the results are strange with your 1648/AAP?
Also, do remember, that drives (when not broken in their read error reporting) report what they see.
They don't report errors on the disc, but errors that they themselves make in reading the disc.
The amount of errors varies from drive to drive (model to model and to a smaller extent, unit to unit).
IMHO, LiteOn models at least since the 1xxx series can sometimes report suspiciously low levels of read errors on discs that are bordering on unreadable on almost any other mainstream dvd reader.
So, take the results (with any single drive) with a grain of salt.