Aie! That was my case too. Please check disc 2 Episode 4. I suspect it's a dual layer thing. I kind of see the infamous cloudy thing and the second layer seems inaccessible.
Just checked my set. All discs load and play with no problems or clouding issues. If I had to pick a disc from the set to go bad it would be Series 1-- I never watch that one.
have you tried cleaning the disk 100% alcohol? So time a thin layer of flim (finger print oil, water residue in humid climates, etc....) can form on single layer disks it will cause series marco checkering and freeze but dual layers will refuse to play or not find certain tracks its happened to me and my friends before and it might look great, but a alcohol cleaning can sometimes get the disk working.