Limbsplit & The Cauteriser 3 socket limit

The limbsplit I bought from someone had it's sockets capped at 3. The text kept saying "Item already has the maximum number of Sockets." I then bought the severed limbs prophecy to upgrade it into the cauteriser but it was still capped at three. I then gave it to my friend to try it out, and he couldnt do anything about it. We ended up bypassing this bug with mastercrafting a 4 socket on it.

Image: https://imgur.com/a/EmNUm

But with Vorici crafting bench you can socket it with 4 sockets (ignoring item level). But you need Vorici to be at least level 4 for that: Vorici - Crafting.