I have exactly the same problem as Lockout_Pin . I'm on a Pixel 6a with an up to date GOS. I newly installed GOS, setup 3 profiles with apps - all with the same 10-digit PIN, NO scrambling, I wrote it down. I used it for 3 days heavily & then all of a sudden the PIN stopped working. I tried logging into other profiles, same thing. I had no other choice other than a factory reset, which I begrudgingly did.
I then repeated the whole setup again installing all apps in 3 profiles, registering apps, same PIN, no scrambling. Used it for 1 day & now I have the same problem!!!! I managed to get in once, & then immediately proceeded to try to change the PIN but it wouldn't accept the current PIN. Then when I tried another profile, I couldn't get in, & eventually got locked out of the Owner profile too.
I am a new GrapheneOS user, an IT Security professional, I use Qubes as my main desktop OS & have 30+ years experience in the industry. Believe me - I am entering the right PIN code, it was saved in Bitwarden.
I really don't know what to do now. I can't be factory resetting & setting this up every few days. Any ideas what's going on?