When I use Dex via my S22 Ultra's USB C port it stops sending a video signal and looses connection with my TV. It turns the video signal on and off fairly often and quickly enogh so I can still use it a bit but it is very annoying. To test it I shut off Dex and Used the phone via mouse and keyboard in Portrait mode on my TV. The signal still cut out but a lot less frequently and came back on fairly quickly. In a further test I tried using Dex on my gaming PC and updated the Dex program and the the Samsung USB driver when I was prompted to do so upon opening it for the first time since the Android / One UI . I have used it over an hour with no incidents happily. I use Dex all the time and it was the main reason I purchased a Samsung phone after owning 3 Google Phones that opperated on Lineage OS. I enjoy using DEX both via USB and in Windows I think it is great . I posted this to see if any other users are experiencing a problem after the update as well.
This happens to me when I plug it in via USB but that's because the main screen goes black on my phone which then disconnects my Dex until I wake up my phone. That was my problem.
