The earliest recollection of this bug is traced back to PAN-OS 8.1.4 - January 09, 2024. This bug is fixed in PAN-OS versions 8.1.4. Fixed an issue in an HA active/active virtual wire configuration where a race condition caused the firewall to intermittently drop First SYN packets when they traversed the HA3 link. For more information: https://docs.paloaltonetworks.com/pan-os/8-1/pan-os-release-notes/pan-os-8-1-addressed-issues/pan-os-8-1-4-addressed-issues