To see if this is the case you can temporary disable the BADTCP feature.
In order to do this, you should connect via SSH and run the following commands:
root@efw:~ # echo ENABLE_BADTCP=off > /var/efw/firewall/settings
root@efw:~ # chown nobody:nogroup /var/efw/firewall/settings
root@efw:~ # jobcontrol restart firewall --force