fwiw, creating a brand new SSID has been completely stable for me now. I re-added all my wireless clients to it and i havent experienced instabilities like I was before (dropouts anywhere between 5min - 4hours requiring modem + router reboots). We'll see how things go, but hopefully OP tried the...
@shadowfiber have you tried making a new network SSID name and re-hooking up your smart devices? I realized I hadn't tried this since it's a chore, naturally. I copied over my old SSID to avoid the process, but wondering if this could be the cause of the issues. Trying it myself, will report...
Created an account just to post here. Having near identical issues to you (AX86u getting constant DHCP errors/ disconnect, also using several smart home products). I've been debugging this for a couple days and have never seen anything like this. Will probably go return the router later today...