My same/similar issue only occurs with NUC ROCK Roon Core HDMI output (5.1 Surround Sound FLAC files stuttering via NUC HDMI output running ROCK) . A separate Ubuntu Sever Roon Bridge endpoint I just added (because of this issue) has no problem at all and neither does my Blu-Ray player or Apple TV. Are you able to test NUC ROCK Roon Core HDMI output with 24bit 88.2khz 6ch (or above) output to see if it exhibits the same issue @zenyatta80 are experiening?