Dolby Vision, Dolby Atmos, and Frequent Buffering Issues on Hisense U8K TV

I have a Hisense U8K Android TV connected via eARC to a Samsung Q990D soundbar, and my media files are original UHD Blu-ray disc rips. When I played Spider-Man 2, HDR activated correctly, but I did not get any audio when Dolby Atmos was selected. I then switched to Talladega Nights: The Ballad of Ricky Bobby, which has both Dolby Vision and Dolby Atmos. In this case, Dolby Atmos audio worked, but Dolby Vision did not activate, and the movie instead played in SDR. I am also experiencing frequent buffering during playback, approximately every 10 seconds, although the exact interval varies. This buffering does not occur when playing the same files through another Jellyfin player, such as Moonfin. In both cases, I verified that the original files were being played directly without switching the bitrate.