Hi and welcome on our forums!
It seems that the second batch of discs you bought are produced by Ritek. Ritek sells media with varying quality (from very good to very crappy). As some players just don't want certain media, chances are great that that's the case here.
Updating with Herrie's firmware? Well you could give it a try. Updating firmware sometimes yields the strangest results...
Please keep us up to date!