Wow - so I'm realizing that when I saw that Vault was still set to Secure - I was actually looking at the EFI on my 1:1 external backup disk. And EFI on my backup I don't even recognize, it's a really scaled down version. I'll have to get to the bottom of this. Probably should have disconnected the external backup disk entirely before doing this.
EDIT: Well, booted up this morning and it froze again. So we're back to square one...
EDIT 2: Going to disconnect my external and see if I get any hangs. Also should note I have Windows installed on a separate internal SATA SSD.
EDIT 3: Haha, nice try. We're still hanging within a few minutes.