powerpc - after the upgrade from v7.4.1, the router drops all incoming vpn connection every 5 minutes or so.

Hello everyone! I need to limit access to hotspot users, so they can only use ONLY Whatsapp and Viber (so after entering username/password, hotspot users could use only Whatsapp/Viber- this is related to very narrow bandwidth). Without hotspot I would normally do this by blocking all traffic in forw...