Can someone confirm or deny this WoC 6.0.2 problem?

When I put video1 (MPEG-2 DVD conform) file in the list of clips to be burned, it's not reencoded again by WoC. When I put video2 in the list, the same happens. No reeencoding by WoC. However as soon as I put 2 or more videos in the list, WoC reencoded every video again (resulting in quality loss). Why is that?

BTW, the videos are set to "Tolerant".

Any help would be appreciated!
Many thanks!