LDW-401S doesn't like second half of discs

I’ve been obsessively watching the X-Files on my computer recently, and every once in a while the second half of the disc will be pretty much unusable on this drive. New drive on another computer plays it flawlessly. 4 episodes per disc, and the 3rd episode is always where the troubles start.

Mostly playback freezes and jumps around, accompanied by corrupted picture. Once I get past a bad area, I can generally go back and it will play fine. Here are two screenshots from Nero discpeed:

If I should be using a different/better diagnostic program, let me know.

Is there any way to force a player to buffer the entire thing before playback or something, if that is the problem? Also, Windows Media Player won’t play the disc at all; it just freezes and alternates between hourglass and cursor very quickly. I am thus using PowerDVD.

Please help, ye who know something about optical drives! :bow: