I'm gonna be honnest, i've burned over 1000 discs but less than 20 DVD9s since they're really expensive in my country. I found some on 40% off and since i've never encountered any problems with Sony discs before i gambled and bought them. (even Verbatim's are rare, they can only be bought online here)
I've always ignored the Layer break options (i'm asumg they kind of merge chapters?) since it worked before without issues.
Guess i'll just have to return them then. Thank you for the reply Lightning and thanks to your ImgBurn I've learned to trust no other, Cheers!