This has been the case to me too, i raised the issue with Jorge and gave him some home work to do.
192.168.174.43 is my server
8102 is the customized non payment portal
Am using API
0 ;;; Redirect No Paying client to the Blocked page
chain=dstnat action=dst-nat to-addresses=192.168.174.43 to-ports=8102 protocol=tcp src-address-list=SpLBL_blocked
1 ;;; Redirect No Paying client to the Blocked page
chain=dstnat action=dst-nat to-addresses=192.168.174.43 to-ports=8102 protocol=tcp src-address-list=SpLBL_blocked dst-port=443
With the two, rules the client is re directed to the nonpayment portal when using mozilla, internet explorer with no hitch but come to chrome, Youtube works non stop + gmail. You will only hit the nonpayment page if you open bbc.com
When i add the third rule as below
2 ;;; cut all other traffic like Peer to peer connections (redirect them to router itself)
chain=dstnat action=redirect protocol=!tcp src-address-list=SpLBL_blocked
Yes Blocked client get no internet but never redirects to the non payment portal!! This rule keeps populating the packets drops
So the client is not aware whether it is a billing or just an internet outage without notice!!