Long short I was at the forge, while it was in it's up state, astarion wandered off the ledge, and survived.
Went and pushed the button at the bottom to move the forge down.
Now it can not be sent up again in any way..
Dubious congrats on being the in the "if I touch the forge in the wrong order, the whole thing gets stuck" club. Search reddit and troubleshoot until you have determined your precise bug. There's a chance that you both cannot fight Grym now (lava valve stuck), and even if you manage to turn the valve, you might only be able to produce one item, so choose carefully.
