My new Panasonic F85 is touchy about playing a select number of disks. Out of forty disks that I've played so far, about two have had trouble with pixelation and momentary freezes in the picture. The disks in question played fine on my previous player, and the Panny F85 seems to play everything else fine. The problem disks never repeat the same pattern of pixelation twice. Is this a bad player, or more likely a case of defective disks?