The earliest recollection of this bug is traced back to PAN-OS 8.1.17 - January 09, 2024. This bug is fixed in PAN-OS versions 9.1.5, 8.1.17. Fixed an issue where the paths between the control plane and the dataplanes in network processing cards (NPCs) stalled in the dataplane-to-control plane direction due to the Ring Descriptor entries becoming out of sync on each side. This produced unrecoverable data path monitoring failures, which caused the chassis to become nonfunctional. For more information: https://docs.paloaltonetworks.com/pan-os/8-1/pan-os-release-notes/pan-os-8-1-addressed-issues/pan-os-8-1-17-addressed-issues https://docs.paloaltonetworks.com/pan-os/9-1/pan-os-release-notes/pan-os-9-1-addressed-issues/pan-os-9-1-5-addressed-issues