WiFi network periodically disappearing or saying "incorrect wifi password"

I have a Xfinity Gateway that has started periodically disconnecting devices from our home network. On some occasions the network appears to have vanished. Other times the net network is visible but when I attempt to rejoin the network I will receive a message like "incorrect wifi password" even when the wifit password has not changed. Restarting the gateway will fix this problem for a seemingly random amount of time (sometimes just minutes) and then the same problem occurs. Running a test of the internet connection usually reports back that the Gateway speeds are correct and connections to devices are strong. A Xfinity technician came out and replaced the gateway but this problem continues to occur. Looking on this forum I saw that others described a seemingly identical problem with xFi Pods (https://forums.xfinity.com/conversations/your-home-network/correct-wifi-password-not-being-recognized/6141f6ba16396f36267ee4cb). I don't own a xFi Pod but we do own a tp-link ac1000 wifi extender. It is unclear to me if the extender is the problem becasue the extender was working without this issues for months before this started happening.

Edit to add: unplugging the extender doesn't seem to fix the issue. We can connect to the main network briefly and then it drops suddenly.