If I understand the documentation on the wiki, all or none of the recipe data should be split per expensiveness level (normal, expensive). This error means that this is not the case for the recipe which was processed (one of the underground belt recipes).
If omnimatter is the only other loaded mod then I think that mod invalidates one of the underground recipes. That would be a bug in omnimatter, not this mod. If I can find some time I can investigate it a little bit, but most likely it's not a bug in this mod.