Getting old router working

I have been having some issues with a new game, R.E.P.O

They seem networking related as I am lagging and then losing connection. Sometimes the game works fine. But usually not.

I have tried using my phone as a hot spot, I have tried a clean install of Windows 10, I have tried another PC.

The issue persists. I want to try another router as a test but its quite old.

It supports VLAN with DD-WRT Firmware. Its an old Linksys WDR2600.

I have eth0 as the wan interface and ath0 ath1 as the wifi then there is vlan 1 and vlan 2 and br0

I managed to get the router to at least think its connected to the internet but I cant access it from my pc/phone. The other issue is my PC lose access to the lan interface and I have to use wifi get back to the router config page.

If anyone has some ideas on how to get this working that be great. My other option as a test is to whack PFSense on my server and use that to test.