Increase the Firewall Maximum Table Entries.
Navigate to System →Advanced → Firewall & NAT.
In Firewall Advanced:
NOTE: This value defines the maximum number of entries that can exist inside of address tables used by the firewall.
These entries include blocked addresses, bogons, aliases, ssh/GUI lockout records, hosts blocked by Suricata / Snort alerts, and so on.
By default this is 200,000 entries; which is usually way too low.
Navigate to Firewall → pfBlockerNG → Update.