Dex mode did take a while for me to figure out. It works best for me when I use the quick settings tile for Dex mode after I connected to a display via HDMI. After that, no other problems except excessive heating and fast battey drain.
My Screen is constantly going black and coming back on when I use DEX via the USB Port. It's goes on and off very often when Dex mode is activated but still usable albeit really annoying. When I shut Dex off and use the the phone in Portrait mode on my TV with mouse and keyboard it still cuts out but a lot less frequently. Dex via windows is working flawlessly so far.....
