The earliest recollection of this bug is traced back to PAN-OS 9.1.9 - July 29, 2024.
This bug is fixed in PAN-OS versions 9.1.9.
Fixed an issue where the routed process stopped responding when the BGP peer sent AS_PATHs with more than 255 AS numbers in all of the segments combined. There can now be a maximum of 255 AS numbers in an AS_PATH list for a prefix.
For more information:
https://docs.paloaltonetworks.com/pan-os/9-1/pan-os-release-notes/pan-os-9-1-addressed-issues/pan-os-9-1-9-addressed-issues