Burning optical media is a balance between good burner and good media. And age is a factor for both.
For example, a marginal burner and good media will often produce a marginal burn.
And the inverse is true, marginal media, good burner.
It takes lots of testing, with plenty of constants (not variables) to discern what's going on. Too many people make knee-jerk reactions that the disc is bad when it is not.
Not only is 12x not too slow, but it's generally suggested over 16x on 16x media.
24x is never suggested.
8x can vary, depending on the burner.
Remember that 16x Verbatim (MCC) media works well, even in realtime (slower than 1x) DVD recorders.
Asus has never made great burners. I have one myself, for ripping/reading only. Even at that task it acts fluky. It's not a good burner. That's what my Pioneer is for.
Software will almost never make a difference. Only something buggy like Nero is a problem, not Prassi. However, look into using
ImgBurn (v2.5.5.0, not newer! spyware!) instead.
Download:
http://www.digitalfaq.com/forum/dvd-...dvdshrink.html
I wonder how long that spindle of discs has been at Rima. MCC 16x media has been around for 10 years now. Although media shelf life does allow for unburned media to survive that long, it's not ideal. There has also been speculation that the discs have changed slightly over time, with a few more coasters than normal about 4-5 years ago.
The crappy/cheap DVD player can also be a problem, not the discs. Some DVD players are really finicky.
I've long since ripped all my discs to drives, and watch DVD images from a WDTV. The discs are in a closet, as backup to the images.