The earliest recollection of this bug is traced back to PAN-OS 8.1.8 - January 09, 2024.
This bug is fixed in PAN-OS versions 8.1.8.
Fixed an issue where packet buffers did not release GlobalProtect clientless VPN packets, which caused the firewall to stop responding.
For more information:
https://docs.paloaltonetworks.com/pan-os/8-1/pan-os-release-notes/pan-os-8-1-addressed-issues/pan-os-8-1-8-addressed-issues