So I think I found what might be a bug. I added the royal gel to a contract and used it. I then went to add another item to one, but it would not let me put them together. I then tried many different items (vanilla and modded, expert and normal, etc.) I could not get any items to combine with the contracts. I'm not sure if this is a bug with only allowing one item, a bug when you used either expert or modded items, or what it is. Like I said, I tried many items, and even tried crashing the game and reloading - but to no avail