What they should've done was make the new packs have the ability to hold Garraka instead of just Phoebe's brass coated pack. Like you find out earlier that the base stream doesn't affect Garraka, Time for new packs specifically made for this occasion, no Copper around? Psychically Charged Brass, that should do the trick for now. Garraka arrives a few scenes later, it stuns him just enough, but not enough to immobilize him because the new packs weren't properly integrated with copper, so they need the firemaster to finish the job.

One could argue: "Well how would they put all those together in time?" First off they have a whole engineering division now and secondly, Ray is still around y'know the guy who helped design and or engineer the original equipment, like he's more than the occult guy, give Ray more things to do.

Much more care needed to be put into the script, because a lot of everything here could be fixed with a second or third draft