I am running 2 X50s in connected via ethernet backhaul in Wifi Router mode with PPPoE connection. I have no issues using the active devices, whether they are connected via ethernet or Wifi. I have Fast Roaming and Beamforming disabled, running Wifi on just 5Ghz where IoT network is on 2.4Ghz. When I reach around 25 devices in the network, idle devices are going offline (Including phones/tablet/TVs along with IoT devices). Both my Samsung device and my wifes Iphone15 or either of our TVs are getting disconnected if left on idle. 

I have tried different Wifi bandwidths, address reservation, fixed MAC adresses etc. to no avail.

For example, my TVs fail to load the next episode because they have already buffered the current episode were idling.

Or when I first open my phone screen, it takes around 5-6 secs for it to actually regain internet access.