Burned DVD is Pixelated

Ok First time here so not sure whether this is even in the right spot.
My son video tapes at the local race track, been doing it now for several weeks but when he taped the race two weeks ago the video came out pixelated (like when a satellite dish loses signal) halfway through. The problem is that he forgot to download the clips to the hard drive and now all we can use to fix it is the dvd that is already burned. I have tried several programs to try to fix this. Power director 8 was used for the edit but now will not open the saved project because the clips are not on the harddrive and the memory card was overwritten with the next race. I have tried video enhancer which after 30 plus hours of trying it did nothing. Also tried dvd rebuilder but everytime I start that program it comes up with some kind of error. Is is possible to re encode the disc itself to make it better. Been using the same discs (memorex lightscribe) with no problems with the earlier dvd’s. I believe this is a problem when it encodes and possibly only recently stared because I was using Express burn trial version and it was getting to the point of expiration. I say this because I used it again for this week and it did the same thing but when I put the files into Nero and burned from there everything is fine. Can this other disc be repaired somehow?

Have you copied the DVD to your hard drive and if so, how does it play from there?

Yes I have and it plays the same.