...are you sure the chip is not just hibernating until next spring?
...I would take the chip for a x-ray at your dentist, just to make sure
it was a connection wire rupture or not, I guess it is a crack at the
silicon. The wires have some slack.
...I believe you can sue Microchip if you can not find the following
text at the technical datasheet:  "Do not drop the chip temperature
faster than 30¡F/second".  :)