The earliest recollection of this bug is traced back to PAN-OS 10.1.3 - July 29, 2024.
This bug is fixed in PAN-OS versions 10.1.3, 9.1.12.
Fixed an issue where the firewall rebooted unexpectedly and displayed the following message: Reboot SYSTEM REBOOT Masterd Initiated .
For more information:
https://docs.paloaltonetworks.com/pan-os/10-1/pan-os-release-notes/pan-os-10-1-3-known-and-addressed-issues/pan-os-10-1-3-addressed-issues
https://docs.paloaltonetworks.com/pan-os/9-1/pan-os-release-notes/pan-os-9-1-addressed-issues/pan-os-9-1-12-addressed-issues