@brand5 VR1210v is an ISP provided device and probably a newer FW release could fix this. Unfortunatelly you can obtain a newer FW release only from your ISP (it they have one) or at least ask them...

@JensenCDenton Archer AX72 is a wireless router and it doesn't include a built-in modem. Despite that, you can still use it to extend your Sky router wireless coverage around you premises. You can...

@MatthewT17 Any home router model can be set in AP mode and configured with the same SSID as your existing AX72 Pro (connected to ER605 LAN port).

@NigaroMatsu For this purpose you'll need a business grade router like these here. ER605 would be a good choice.

@TTurtle Archer AX50 doesn't have a wireless repeater feature implemented - it only has AP mode (Case 1) feature. It also doesn't support any mesh feature, but you can still name its SSID the same as...

@brand5 A similar behavior could be observed if the router has its UPnP feature enabled. Disable UPnP and reboot the router, then try to port-forward TCP 80 again.