Are you sure the other DVDs are -R?
Hi another expert here to try to assist.
I would like to ask you to check on the DVD speed on the ones that were working and the one that do not work. On top of the DVD, there is a maximum writing speed indicated by a number and X next to it. For example mine are showing 16X.
This will help me understand to whether the problem is related to dvd writing speed or not.