Nexus 7 - pin lock corruption?

[#1]

I can't believe this.
My Nexus 7 has just decided that it doesn't like my lock screen PIN (all I get is "Wrong PIN"). The PIN was set months ago, and I haven't changed it - in fact, I entered it without issue literally 5 minutes before it all went wrong (and it's been entered so many times that it's in my muscle memory!). Literally the only thing I did was connect up my Bluetooth keyboard (which I haven't used for a while), went away to make a coffee, came back, tried to enter the PIN on the Bluetooth keyboard and it failed. Figuring I must have typed it wrong, I tried again, "Wrong PIN". Tried on the on-screen keypad - "Wrong PIN".
To top it all off, I don't get offered any chance of resetting the PIN - just 30 second delays every 5 failed attempts. Rebooting didn't help.

[#2]

If you keep entering it, (may have to do it half a dozen times or so) eventually it will give you the option to sign in with your Google login .

[#3]

Thanks. By all accounts It should do that, but it isn't. Now up to 105 attempts, according to the on screen message.
Edit: I ended up doing a factory reset. Good job there wasn't anything on the tablet that isn't stored elsewhere.

[#4]

You were lucky it isn't a Nexus 6. 

[#5]

Quote from: CX

Thanks. By all accounts It should do that, but it isn't. Now up to 105 attempts, according to the on screen message.

Strange, that worked for me in the past.
Edit, appears it only works if WiFi is enabled, which I guess makes sense since i presume it would have to authenticate with googles servers.