I am impressed your trying in Router Mode on your SH.
-- Red (VM SH2 AC Beta tester) Running on 1Gbps VM service with SH4 in Modem Mode, with a ASUS GT-AX6000 router. With this setup I get Fantastic WIRED and WIRELESS Signals in my home. I dont work for VM. But I work in IT, and I know my tech. My advice is at your own risk. If you are happy with my answers please press Kudo ?
@Blacknun With two consoles on the same LAN they will often be using the same ports, especially two from the same company, so you need a router that does a good job of managing UPNP in order to ensure the correct incoming packets go to the correct console. Unfortunately the VM hubs do not have a good reputation when it comes to UPNP. Switching off UPNP in the hub is definitely not going to help.
The best solution is usually to get a third party router that does handle UPNP properly and put the VM hub into modem mode. The Netgear R7000 router that I use has been recommended on PlayStation and Xbox forums over the years as being good for households with multiple consoles, but I'm sure there are many others that are equally good.
Alternatively I believe some people have had success by putting one of their consoles in the DMZ and setting up port forwarding for the other one. Not tried that personally and putting the PS4 in the DMZ may result in a warning letter from VM about a MDNS vulnerability due to the way the Spotify client on the console works (or at least worked previously):