The earliest recollection of this bug is traced back to PAN-OS 11.2.10 - March 31, 2026. This bug is fixed in PAN-OS versions 11.2.7-h12, 11.2.11, 11.2.10-h5, 12.1.6. Fixed an issue where, when Advanced DNS Security was enabled and experienced unusually high loads, DNS resolution failures occurred with the error resources-unavailable . When Advanced DNS Security is enabled and experiences unusually high loads, DNS traffic sessions may be impacted, resulting in DNS resolution failures. Traffic logs for these sessions show an end-reason of resources-unavailable . Workaround: Disable Advanced DNS Security telemetry ( Device Setup Content-ID Advanced DNS Security and uncheck Telemetry Enable ). For more information: https://docs.paloaltonetworks.com/ngfw/release-notes/12-1/pan-os-12-1-6-known-and-addressed-issues/pan-os-12-1-6-addressed-issues https://docs.paloaltonetworks.com/pan-os/11-2/pan-os-release-notes/pan-os-11-2-10-known-and-addressed-issues/pan-os-11-2-10-h5-addressed-issues https://docs.paloaltonetworks.com/pan-os/11-2/pan-os-release-notes/pan-os-11-2-10-known-and-addressed-issues/pan-os-11-2-10-known-issues https://docs.paloaltonetworks.com/pan-os/11-2/pan-os-release-notes/pan-os-11-2-11-known-and-addressed-issues/pan-os-11-2-11-addressed-issues https://docs.paloaltonetworks.com/pan-os/11-2/pan-os-release-notes/pan-os-11-2-7-known-and-addressed-issues/pan-os-11-2-7-h12-addressed-issues https://docs.paloaltonetworks.com/pan-os/11-2/pan-os-release-notes/pan-os-11-2-7-known-and-addressed-issues/pan-os-11-2-7-known-issues https://docs.paloaltonetworks.com/pan-os/11-2/pan-os-release-notes/pan-os-11-2-8-known-and-addressed-issues/pan-os-11-2-8-known-issues https://docs.paloaltonetworks.com/pan-os/11-2/pan-os-release-notes/pan-os-11-2-9-known-and-addressed-issues/pan-os-11-2-9-known-issues