Possibly stop machine from functioning until there is sufficient space for more items within its inventory

What version is this happening on?

1.1.131

And also happening on the hammers.....

I think I found the issue. When you check all slots to see if they have content and so stop the machine, you are checking ALL inventory slots, including the ones used for bonus (hammers/enchanted books).

If these slots are empty, it assumes it always have space and tries to process the item, resulting in spilling.