@scraph . After reading your problem description and assuming you haven't changed anything in the last few week in your network, the only thing that has been changed is your AX4400 FW version. I...

@7714-7e Check your WAN port negotiation speed here: Scroll down to the bottom of this page: Check if the negotiated speed is correct., Do you have any other modem/router before AXE75 like (any ISP...

@casa26687 That's very important setting, Asus Automatic equivalent in TP-Link is Dynamic IP: Most probably, if your ARRIS SB6183 has a LAN IP address 192.168.100.1 it's set in bridge mode or it's a...

@casa26687 To have an internet on your new AXE75 you should copy Asus WAN (internet) port settings to the AXE75 WAN port. This includes Internet connection type, any username/password, etc. You might...

@scraph Have you tried to reset the AX4400 and re-add to the Archer BE550 Essymesh. If you haven't, try that and check if there's any imrovement in stability. If there's no improvement, the other...

@gandalf1369 It's correct as long as you use the WAN port of the router. The scenario I was pointing out is if you use Case 2 from this FAQ - apparently that's not your case. The last resort would be...