I agree with Dialysis and sneaksone...this is very likely a VSO problem (Fab's default burn engine).
While Img isn't quite as well integrated in Fab, you can still have completely seamless SL burns. You will still have to choose a layer break location on DL burns, but Img will populate a list for you you and it only requires a click of the mouse. ..a small price to pay for a top-notch burn engine.
Img will also afford much greater configurablity. For eg., spend a few minutes to set up media and burn speeds and Img will remember this and burn a specific media in a particular burner and at a selected speed...everytime.
Please make the following change in Img to configure seamless SL burns:
tools > settings > build > don't prompt image details
BTW, I'm a huge fan of "lazy"...