When smelting 64 of an item with exactly 8 coal, occasionally, only 63 items are smelted and 1 item is left unsmelted. Does not happen in Vanilla.

Steps to Reproduce:

1. Place 16 furnaces.
2. Fill furnaces with 64 of an unsmelted material.
3. Place 8 coal in each furnace.
4. Wait.
5. Check furnaces. Some will have smelted the full stack while others only 63.