Been struggling the last few days with devices on my network, after the AX55 has been running solidly for 2 yrs with no issues.

I have auto-update on the firmware and am running the latest, but not sure exactly when it last updated.

I have an 'average' houseload of devices - 2 chromecasts, 4 wifi lights and 2 wifi powerpoints, ipads, kids phones, and a few wired and wireless PCs and laptops. Oh, and the kids' friends' laptops and phones because they all need free wifi of course :-) I have both 5 and 2.4 ghz wifi configured.

Suddenly the other day, the majority of devices (wired and wireless) were not able to get IP addresses.

I looked at my DHCP leases and noticed that many of them were very high in the range so I thought maybe I was running out of addresses. Odd.

So I expanded the DHCP subnet mask from 255.255.255.0 to 255.255.252.0 figuring that would give me more IP addresses. It certainly did. 

After numerous reboots to clean out leases this mostly cleared things up, but now I'm at a point where most devices can connect (maybe 85%), but not everything.

In particular, iPhones are fine, iPads struggle but eventually connect, and samsung galaxy phones (2 of them) won't connect at all. Windows laptops are hit and miss. 

Interestingly, if I manually override a spare IP address, subnet mask (255.255.252.0), gateway (192.168.0.1) and DNS (192.168.0.1) into the client device (eg my windows laptop), it connects and seems to work fine.

What am I missing?

Thanks!!