This is a bug I've encountered on the normal mod version aswell, but if an item made with combination crafting requires a very large amount of energy in total to craft (i assume the limit is 2.147 billion), the item will never finish crafting, it will just forever keep using energy. Using Integrated Dynamics to read the nbt of the crafting core quickly, it is possible to see that the 'Progress' value constantly switches between negative and positive numbers, which I assume is because of the integer limit.