Did you check if the interfaces are up when it's not working? Check the log files. Maybe ifplugd is bringing one or both interfaces down, in that case you can disable it in /etc/default/ifplugd.

I found that it's not an issue confined to the RPi. I built and installed the 8192cu (nor rtl8192) driver from here: https://github.com/pvaret/rtl8192cu-fixes which is basically a port of the same driver that is included in the RPi 4.0.x kernel. When I load that in a Ubuntu VM it behaves the same wa...

You have both interfaces on the same subnet (192.168.1/24). This is often a cause for trouble. From where are you trying t access the RPi? From the same subnet, that is does the host you are coming from have an 192.168.1.* address as well? If not, then my guess is that wlan0 doesn't have the default...

I just purchased the Alfa AWUS036NHR. My plan is to use it to build an access point/router with the RPi. It already works with two Edimax dongles: one acts as a client, the other as an AP. The setup is very stable, using the stock wpa_supplicant from raspbian and the hostapd from https://github.com/...