My opinion is a media issue.
However, it is difficult for us to understand what's happening if you don't give details about the media that gives you troubles. DVD Identifier can help you.
Once you know the exact media code (e.g. TYG01, MCC003, ecc), you can check by yourself in the Black DVD Media Tests subforum how it behaves in various situations.
Unfortunately, both the PX-708 and the PX-740 can not perform quality check tests (unless you want to try something with BenQ firmware that will void the warranty of your 740 drive :bigsmile: ).
About the DVDs you weren't able to read back with the 740... are they of the same brand/batch of those that you are able to read back now? Or are they different?
And when you say "If I try to read with my PX-708 drive (1.08), no problems at all", can you be more specific? I understand that you are able to read back them, but in which way? Did you read them back completely, without aborting the process? (you have more chance to get read problems at the end of the process, on the outer part of the disc) Do you notice slowdowns during the read process? Can you try to do a transfer rate test, e.g. using Nero CD/DVD Speed? If yes, do you get a "smooth" curve or do you notice some slowdowns?
Just a bunch of ideas...
Ah, one last remark: I suggest to apply newer firmware 1.01 to your 740, it fixed some quality problems with 16x burns of MCC004 media.
Welcome to the forums!