I have built updated packages.
Temporary instructions:
yum update http://packages.nethserver.org/nethserver/7.4.1708/autobuild/x86_64/Packages/nethserver-firewall-base-3.3.1-1.5.pr60.g12598d4.ns7.noarch.rpm http://packages.nethserver.org/nethserver/7.4.1708/autobuild/x86_64/Packages/nethserver-firewall-base-ui-3.3.1-1.5.pr60.g12598d4.ns7.noarch.rpm
config setprop firewall tc Internal
signal-event firewall-adjust
I suggest setting ingress (inbound/download) bandwidth to empty or zero. If you put a limit on ingress (why?), you may need to disable advanced features on some ethernet cards.
ethtool -K $IF tso off
ethtool -K $IF gso off
Substitute $IF with the wan (red) interface name.