6 bits of leather in inventory + 2 Bees wax.
Cauldron on the boil. "Craft-all" Hard Leather.
First piece of Hard Leather is made.
2nd piece of hard is made - but first piece of Hard Leather disappears and I'm left with 1 bit of Normal Leather and 1 piece of Hard Leather in my inventory.
It seems that after making each piece of Hard Leather, I have to put it safely away so it doesn't get nabbed to make the next one.