Yes yes yes I've been struggling with this for months. I've tried to figure out food intolarences etc.
now I don't struggle with it very often anymore but I sometimes do. I THINK that it might actually be the fat. And I understand you think this is not the case because you can eat large amounts of fat. For me it was the same. But I figured out I couldn't handle very concentrated sources of fat. Nuts, chocolate, cheese etc in large amounts. Because it's almost all fat. But at the same time I could eat MORE fat in total by eating e.g. beef because it's not as concentrated . Good luck