I hate to cry wolf, but this looks new. Reduced rip speed problem

I have been doing some testing of drive ripping and I think I have found something new. I have ripped a number of DL discs on all of my drives and they all rip as expected…until now. I have now found two of my discs that will rip only at very slow speeds on 3 drives and will rip normally on the fourth. The problem DL disc starts at 1.3X on my BenQ with the speed hack, starts at 2X on my LG and close to there on my Liteon. On all of these drives it slowly rises and never really gets much above 4X or 5X. On other DL discs all three of these drives rip 3-4 times faster. I experienced similar slow downs on another new disc that happens to be SL.

None of these drives have any problem reading the discs. If I run them through DVD Shrink I get the same slow down. None of these drives will do a CD Speed transfer scan as I get the error message, READ OF SCRAMBLED SECTOR WITHOUT AUTHENTICATION

None of this happens when I use the AOpen 1648.

Either I have two very different discs with a very coincidental pressing flaw (through the entire disc) or there is some new system slowing down my ripping. As I only tripped across this recently as I almost always rip with the AOpen, there may be more discs in my collection with similar slowdown.

Anyone else seen this?