NFQUEUE is a kernel and user mode module for managing network packets in iptables.
The following event is seen along with a noticeable impact on system resources especially on PCS 9.1R5 and in some rare cases may show up on any PCS version from 9.0R1 onwards as well.
2020-05-12 01:31:40 - PSA7000 - [127.0.0.1] System() - Nfqueue is full and dropping packets. (kernel).
This issue is known to occur on PCS versions that support FQDN ACLs irrespective of it being configured or not.
This feature to configure "FQDN Resources" under Users -> Resource Policies -> VPN Tunneling Access Control, was introduced in PCS 9.0R1.