@songjixian, PA-500s are getting up there and you could be running into an actual hardware issue. That being said, this error can also simply be caused by a software issue. I would try to either revert if you just did a software upgrade and switch over to the other partition using the debug swm revert aftger you've verified that your sysroot partition is revertable through debug swm status to see if that fixes your issue. If the revert doesn't fix the issue the next step would be a factory reset through maintenance mode, and if that still doesn't work then it would be a likely hardware issue with the PA-500.
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