YES there is a video problem on disc 4:
Episode 19, "Crisis" on disc #4.
Chapter 3 (title 5) from around 17:40 to around 23:00 (the chapter's end) and on chapter 5 (the preview)
Heavy interlacing, visible scan lines, jerky/jittery animation. A fair number of people (myself included) have this problem. It is a glitchy disc.
Contact ADV and they will send you a generic form. Fill the form out and ship it along with the ENTIRE package (so yes that includes the multi-disc case and booklet). You pay for shipping to ADV and they will ship a new one at their expense. This info is straight from an ADV rep.
I have not sent mine back b/c i am waiting for an official response on this issue (i.e. have they gone back and remastered it? was it just a small batch which has this error? etc). When I asked ADV if the new discs will be corrected they didn't really answer me. I would hate to send this back and get another bad disc.