IPFire is a statefull firewall that uses connection tracking.
The conntrack table has 262144 entries on systems with more than 4GB Ram. (Linux kernel default)
https://www.kernel.org/doc/html/latest/networking/nf_conntrack-sysctl.html
ty to increase net.nf_conntrack_max
sysctl -w net.nf_conntrack_max=524288