Here's my Facom adjustables, none I've bought new, the 2nd and 4th were replaced no quibble, as I use them to tighten propellors, on boats, and yeah I use a lump hammer, and eventually they can slip.
I always wanted a med size set of ally pipe grips.....
bought a nice set from Cromwel.....all ally and still going well.....
perhaps u coud look there for ur spare Jaws.....