Ayu DVD sound quality.

[edgefusion]

First off, sorry if this in the wrong section but I didn't know where else to put it and I really want some help.

Basically, the sound quality on all my Ayu DVDs (Arena Tour, Albums etc.) degrades as time goes on. Like, I'll put in the DVD and start playing it and it'll sound fine, but it'll keep getting worse until it sounds all scratchy and bad (I can't listen to Ayu like this!). It's not permanent and if I restart the dvd player it sounds good again (for all of a minute until it starts to re-degrade). I've tried it on my PS2 and on my mums DVD player and the problem is still there (and it's only on Ayu discs, all others are fine). However if I play these discs on my computer there is no problem, the sound quality stays consistently great!

I thought at first it was the region coding that was doing it but I'm in Europe which is region 2, the same as Japan so that can't be it.

Any ideas??