Yes, recently I have unsuccessfully tried many security code combinations on an old Nokia Asha 311 phone that I wanted to resuscitate for some tests, losing a few hours trying. I was thinking that a few years ago I must have selected a code that was also in my current list of possible codes! And eventually I found out that indeed, that was the case, but (re-)discovering the correct value required me to understand two things:
- Security code has 5 digits, so I shouldn’t have tried 4 digit PINs (nor 6 digit values).
- After unsuccessfully trying with 2 (or 3?) codes, I should have shut down and restarted the phone before trying again with other values.
If one does not restart the phone (personally I removed the battery to be sure) after each small set of subsequent failures, it seems that a special security by obscurity feature comes into action, and then any combination – even the correct code – would eventually fail with the same security code error. (This is to avoid brute force attacks, I guess.)