I ended up in this same situation, completely locked out of my keychain access after updating to golden gate and i have to restart. Loading a backed-up keychain fails and my login password isn't suitable (why would my login keychain not be my computer password is beyond me.) i have a feeling it has to do with the entropy file. im not sure why this failed completely w/ golden gate and trying to work with an older one requires disabling SIP which is ... scary. At some point, I think i was running into a locked keychain on tahoe and changing my user password to the same password would make it work again. I'm close to just loading tahoe up again or just giving up and restarting :/