It works fine for me. Try out clearing the cache on your One UI Home app you can do this by going to Settings-Apps-One UI Home-Storage-Clear Cache. Then maybe try doing the normal procedure of mirroring your device or otherwise known as Smart View. Press Smart View-Find your correct TV to pair with and it should work with your Q series because mine worked, but every device acts differently so it might or might not. If you are talking about Youtubes own Screen Mirroring, it works fine on mine.
Please try the suggestions made by @PrimePixel . If the issue persists, please send us an error report from the Samsung member’s app -> Beta Feedback -> Error Reports. We apologize for the inconvenience and appreciate your contribution to the beta program.
