I tried to break down the Vending Upgrade in Omnifactory, just to see what is required. But once the number of ingredients is greater than a hundred or slow, the calculator would be very slow. It would take around 5 seconds to load or close, or to import any new recipes. However, if I switched to a new recipe, the issues were gone. Gameplay was not otherwise affected.

Yes, the lag is caused by calculation of the selected item. Once you change the item, the lag is gone. I know the performance problem for a long time, and it's caused by a very high time complexity of CostList merging. I have searched for some algorithms for a descent improvement, but have no time for it. It's always the top priority on my long term todo list.