Flashback arrestor leaking.
 

So ordered thru mountain glass. First time hooking it up. And there's a leak at the threads between the regulator. The question I have is can I just thread tape the threads and fix it or should I just not mess with it and get a new fba

I would call MG and talk to them. If it is truly defective, they would want to know about it I bet.

All those parts are made from really soft brass and if you "gronk" too hard on them they will leak.

Yellow teflon tape might get you by once or twice but if the tape doesn't seal the joint past the bubble test then one part or both are toast.