I have same setup: GS5 KitKat, TWC Roadrunner Turbo, and ARRIS modem/router. I think I fixed it by disabling ipv6 on ARRIS modem.
you have to uncheck "Enable DHCP (IPV6)" under DYNAMIC (IPV6) & uncheck "Enable Static IPV6" under STATIC (IPV6) on the WAN Setup tab, and also uncheck "Enable DHCP...