Hello,
I was adding a sturdy shield to a player's character and it wasn't working correctly after adding it to the inventory and equipping it. It wouldn't apply the armor class bonus when raising the shield. I think this is because it is of the category "Shields" and not "Shield".
Comparing a Steel shield to a Sturdy shield you'll see that the sturdy shield doesn't list an AC bonus, hardness, HP and BT:
Attachment 36658
Attachment 36659
After adding the sturdy shield to the inventory, unlocking it, changing the Category to "Shield", locking and unlocking it again, I could enter the required data. I think it would be preferable if it applied the right bonusses right away? ;)