Right i download & burn off dvds all the time when i can

A problem has turnt up.. my mate asked for a film (hills have eyes 2) put it in the pc started my magic disk copier & it says there is no dvd disk in drive then i started dvd decryter & that says disk empty! so whacked it in my dvd player & it played, so then whacked in back in the pc & it played! but if i go to copy it, it says disk is empty WTF!!!

So i tryed out many of my copied films & its 50/50, half of my stash can be re-copied & the other half cant that i tryed out!

Now im like WTF! i've burnt all my dvds the same way since i done my very first one, im brainless on this one.. who else is???