I have a Plextor Premium drive which is supposed to be a 2 sheep drive. As has been indicated in other threads in other forums, there is some controversy about the Plextor being able to backup Safedisc 2.9. To get around the problem I enabled "Bypass EFM Errors" in Alcohol and my backup seems to now work great in all my drives.
If it requires Bypass efm error to make a good back-up, your particular writer is not a true 2 sheep model (though it must be recognised that not all writers generally regarded as 2 sheep models can cope with sd 2.9).
Does enabling "Bypass EFM Errors" require that the computer on which the backup is run have Alcohol installed?
Briefly, what does "Bypass EFM Errors" do?
It enhances the weak sectors [same as AWS in CloneCD, EWS in Blindwrite and SAM in CD-Mate]. This frequently enables 1 sheep and occasionally 0 sheep writers to make working copies of safedisc 2.51+ protected cds which they would not otherwise be able to do.