The first password (around day 6 for everyone but Roswell i think) is different for each character and is found in the bad endings look for a word that stands out from the others.
Each password can usually be found in the bad endings and if it isn't in there it's usually in the same day you go to the vault.
No problem the first few times you go to the vault are just for easter eggs and for Grizz to test stuff so the vault works the way it's meant too.
Also a few other things :
When you can look at the name of the coffee cup just put 'Dave'. The cup isn't for changing your name it unlocks some easter eggs but otherwise it just gives you +1 affection with whatever character's name is on it. Putting 'Dave' gives +1 to everyone which can help if you want to get some of the better interactions like hugging someone when they're sad.
The choice that locks in what route you are on is when you pick who your partner is for the scavenger hunt.
