Issue with backing up movies

Ok let me start off saying I have been backing up movies for a long time but I seem to have some wierd issues and I know I am not alone as the guys I work with have the same issue.
Here is the apps I use to back up movies:

  1. dvd shrink
  2. Dvd decrypter
  3. Dvd 2to one
    I use nothing but the best media:
  4. Verbatim
  5. TY
  6. TDK
    Here is the problem I backup one of my kids movies and file the master copy away, They watch it a couple of times I always handle the movie not them.
    A couple of months go by and they want to watch it again and it pauses or stops in every DVD player in the house. There are no scratches on it They look brand new.
    Here is a list of my hardware: I don’t remember the exact model numbers.
    Oppo Top model
    Play station 2

DVD burners:
Plextor 712a
Nec7170 New

I did run quallity scans on some (Spot check) and they all looked real good.
Does anyone know why this would happen? sometimes I can copy the files off of the media and make a new copy and all is well but sometimes I will get crc errors and I have to ditch the disk and make a new copy from the original.
I build a new pc about every year so I know it’s not my box, I also upgrade my burner often as I have had many burners not listed in this post and the same problem persists. Since I know others who have this issue I am perplexed as to what is going on. Does anyone else have this issue here. Thanks in advance for any help.