I noticed since I started using the Sony brand that I get some jumbled up blocks? I've had that happen with non-backed up movies before to. Does it sound like a buring problem/disc/or the DVD needs another cleaning?
What drive are you using when you see those jumbled blocks? This is called pixellation. Several reasons for this on backups: Media quality-usually the low quality manufactures. Burned too fast. Too much compression Dirty laser lens on the drive that shows those issues Paper/sticker labels And many more possibilities. Since you are getting that pixellation on both backups and originals,I'd say it's the drive that shows these issues may need a lens cleaning. That lens cleaning is a last resort-before replacement.Your discs should always be clean before inserting into drives. Try them on some other drives and see how they look.