I take that back: the problem is unrelated to the Broadcom. I figured out that if I push too hard in the middle of the keyboard, the system instantly crashes as I described. So I'm thinking I bumped something or knocked a connection loose while swapping the cards.
Thanks again for the Broadcom tip though, now that I know that's not causing my current problem lol
If anyone from Intel is still in the thread I can provide the minidump report (it's a stop error 124: WHEA_UNCORRECTABLE_ERROR)