[tfwnopmt]

For the security model to work, the information has to be irretrievable if the security chip breaks. Otherwise a motivated party can simply solder-on a new security chip to get into a locked phone, or compel google to give up the keys.

I suggest you look into reflowing the security chip. Chances are that it's a solder failure, rather than something more difficult like electromigration or something inside the chip.