GFCIs can be a booger to diagnose. Your outlets in your bathroom could be causing interference with the breaker itself. Or the breaker could be causing your issues. I've heard nothing but bad things about GFCI breakers. Costly to replace, and they're junk.
I have tripped a GFCI in a completely...
Engineers and welding dont belong in the same sentence unless "dont know s***about" is between them.
They call us when they have a question about welding and writing a weld procedure lol.
Cast is an entirely animal. There are multiple types and compositions of cast iron (white iron in particle is unweldable). Without knowing that composition you are quite literally guessing whether or not you are using the correct filler material and procedure. Not all cast calls for high nickel...
You will need someone who knows what they are doing and even then its a crap shoot if it holds.
Cast can be pretty fickle. It will need to be prepped and preheated correctly as well as cooled correctly to prevent cracking the weld.
I can tell you its hit and miss what holds and what doesn't...