My advice is to return the disks as defective. If enough people do this, maybe we'll see fewer of these threads.
We get complaints about DL media every day in these forums. Usually Memorex, or TDK, or Sony...any of those that use the Ritek or Ricoh DL disks made in Taiwan.
The only DL media we recommend as consistently good and easily found is sold under the Verbatim brand.