What do you mean it is the first time you updated it? Did you already have GOS 18 months ago, but only updated yesterday? Maybe, there’s a bug due to that?
You say that you’re using a PIN: is it really a PIN, not a password? How long?
When entering your PIN, are you sure that all the inputs are taken into account?
Maybe I did miss something, but it doesn’t make sense to me to factory reset without question when you’re sure of your PIN. Let’s say you had the same six-digit PIN for the last year: it’s hard to believe that you forgot it just like that. Maybe think about something else for a few days, in the case you’re misremembering it.
Or there’s a bug with the keyboard…