I have a pair of these units, one downstairs connected to the cable modem and doing the NAT routing and DHCP.  The one upstaris is set to Access Point mode, and I have done my best to configure the wireless the same between the two to allow for roaming (Sames SSID, Security, etc..).  The problem is that I keep getting "Authenticain error" on the WIFI devices, they will work for a while then suddenly pop up the message.  It's happening on phones, tablets and Windows & Linux PCs.  The wired ones don't have the problem, just the WIFI connected ones.  I have been reading the threads on this, and they seem to think it's somehting to do with the ISP.  I don't think so, as I said anything connted through the AX1500 on a wired connection hums right along with no problems, it's just the WIFI ones.   Somehting isn't right with the WPA2 is my guess.  It's not limited to specific WIFI clients, so that points back to the routers as the common element.  These are an upgrade from an ASUS pair of 802.11AC routers set up pretty much the same way that never had a problem.