Hello all, I hope you can help me as I am really baffled.
I had an accident with my FP3, dropped in water and didn’t work any more. It booted, but display was dead. So I ordered a display module replacement, which promptly arrived, and changed it.
All good, the phone starts and everything seems back to normal, it connects to the internet, shows my new notifications, etc…
BUT
It asks for a PIN, required after restart, and my old PIN does not work anymore…
I am sure I am typing it right, it’s not the SIM PIN, because it happens also without SIMs, and in any case it lets my try too many times for a SIM PIN.
Could something trigger a screen lock PIN change?
Either the water accident (but everything seems to be working), or the display module change, or the disassembly.
Any suggestions?
I obv. don’t want to do a factory reset
Welcome to the community forum!
It is unlikely that the module swap caused your PIN problem. Without knowing any more details my best guess is that water damage lead to some sort of data corruption, perhaps. This might then lead to failure when trying to unlock the data partition. In that case it’s not really like the PIN changed somehow, but rather that it can simply not be verified any more. If this were the case, then your data is likely already lost and a factory reset might be the only option left, unfortunately. 
thank you for your reply, yes the data corruption was my first thought too, but I see everything else working fine (I cannot enter the phone, but its behaviour suggests that it’s able to retrieve credentials, connect, etc etc). That the data damage impacted only the screen lock seems a very unlikely scenario…
It would be nice to understand how does the screen lock code/pattern encryption and storage works. I suspect it may take a fingerprint of the system’s hardware to avoid tampering, and maybe now that one component has been replaced the computed hash is different?
I’ll keep troubleshooting, trying to avoid the factory reset.
Btw, I was pretty sure I had smart lock enabled too, and that also does not work.
In the end, I gave up and did a factory reset.
Interestingly, as part of the data import from the cloud after the reset, Google asked for the last screen-lock code, which was correct. And the phone storage didn’t have any damage, it’s working fine after the format of the data partition.
I am intrigued that Google could validate the last screen-lock code. It means that it is stored in the cloud, but also locally (given that obviously you can unlock your phone while offline).
A part for a temporary data corruption of the local screen-lock storage, the only other explanation that I can think of is related to the malfunctioning of the touch screen. When the display was about to die, it was generating all sort of numbers as an input to the screen lock. I suspect this may have create some overflow or something like that, and corrupted to local screen-lock. Weird.
Usually codes or passwords are not stored anywhere. Hash codes generated from them are, so that storage holds a one-way means to check them for validity without holding the codes or passwords themselves.
Just preventing the next big internet outrage 
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