I think I might know how to get into the bunker, but I don't have the item needed to test that theory.
I would've gotten the item for free, but it seems like the freebie near Yankee was removed, or moved to a different location entirely.
Being vague for the mystery of it... Also, the so called "Password Changer" got the (WIP) text removed, it isn't the original item I had planned but what's up with that?