The earliest recollection of this bug is traced back to PAN-OS 8.1.12 - January 08, 2024.
This bug is fixed in PAN-OS versions 8.1.12.
( PA-7000 Series firewalls only ) Fixed an issue where internal path monitoring failures occurred due to either a buffer leak or buffer corruption.
For more information:
https://docs.paloaltonetworks.com/pan-os/8-1/pan-os-release-notes/pan-os-8-1-addressed-issues/pan-os-8-1-12-addressed-issues