I have an RE205 extender that I've had for about a year, and has mostly worked totally fine in that time. In the last few days however, I've started having issues with it and my iPhone 12 (iOS 14.7.1). It will be working, and then suddenly the internet connection will fail—if I look in the Wifi settings on the phone, it'll be connected to the network but show me the orange alert that says "No Internet Connection".
While this is going on, other devices that are connected to the extender's network in the same room as the phone (a MacBook and a TCL TV) have a strong signal and work perfectly fine. I can also connect my phone directly to the router's network, and to a separate extension network from another RE205, and both work fine. If I restart the problematic extender by unplugging and replugging it, it'll work with my phone for a few minutes, and then the internet connection will drop again.
I've tried checking for a firmware update via the app and it says it's up to date. I've also restarted the iPhone, and the issue persists.