The media is your problem <> Bad media always causes problems at the end of a disk.
I use Ritek but If u use cheapo's u get bad results.
Another tip is when compressing your DVD before burning make it around 4.3 GB then U will not burn right to the edge of a DVDR & it will lessen the chance of films being crap at the end.
Of course another thing causes no ending & that is a greasy thumbprint on the edge of the DVD.