Multi Color Macadamia Nuts After Roasting

Hello,

So still fairly new to roasting nuts, I was brought a few macadamia nuts that have been roasted and show different colors of brown within the nut. It can be all white with a brown spot, or you can see layers of different browns. The smell is a little different and there are no discoloration when they are raw. Only a handful of the nuts are affected but my question is what causes it? I googled with no luck. If they were burnt or over roasted more would be this way. We also stir the nuts while roasting and it is a dry roast. 

Well, saw this at a nut roaster and they determined their equipment was out of balance and thus they were gettng spot burns, they made adjustments and it stopped. They also stir (automatic stir.)

The owner said it had something to do with its natural oils. I need to keep looking. He was brave enough to taste them and said they tasted fine.