It won’t be of any help to you because the C2 has no recovery mode, but the device permanently locking itself without you (probably) having done anything sounds a lot like a (never fixed) bug I experienced years ago on the Jolla Tablet, which suddenly decided my lock code was no longer correct and then claimed it was permanently locked, but then after lots of reboots suddenly decided the code was correct after all and it was no longer permanently locked:
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