The earliest recollection of this bug is traced back to PAN-OS 8.1.13 - January 09, 2024. This bug is fixed in PAN-OS versions 8.1.13. Fixed an issue where GPRS tunneling protocol (GTP) version 2 handling was unable to handle fully qualified tunnel endpoint IDs (FTEID) coming in reverse order, leading to GTP-C and GTP-U flows with incorrect IP addresses and tunnel endpoint IDs (TEIDs). This caused a GTP stateful inspection failure for further packets on the respective flows. For more information: https://docs.paloaltonetworks.com/pan-os/8-1/pan-os-release-notes/pan-os-8-1-addressed-issues/pan-os-8-1-13-addressed-issues