The earliest recollection of this bug is traced back to PAN-OS 9.1.10 - July 29, 2024. This bug is fixed in PAN-OS versions 9.1.10. Fixed an intermittent issue where, when the DNS Security cloud was not reachable, DNS responses had bad UDP checksums. For more information: https://docs.paloaltonetworks.com/pan-os/9-1/pan-os-release-notes/pan-os-9-1-addressed-issues/pan-os-9-1-10-addressed-issues