Changing ranks works fine for all groups expect for Sergeant First Class -> Master Sergeant
I have no idea why those specific groups, there are other near identical ones that do work.

http://pastebin.com/cZUsvuya

permissions (PEX):
http://pastebin.com/rQB7jiDe

Thanks for the bug report, but this isn't a Vault issue at all. It's either something with PEX or how you have your groups setup.

I redid my permissions config and now it seems to be working, not sure what I did wrong the first time.
Sorry for bothering you with this, <3 Vault ;)

no problem, glad you got it fixed.