Xbox one X Atmos issues

Ashy9

Hi can anyone help I own Xbox one x and have it connected to my new Atmos soundbar got the Dolby app and have it set to bitstream for Atmos I have no issues with Atmos 4k films.However when I want to watch a standard Blu-ray and the film starts the sound goes off for a while I also get a loud cracking sound between inputs which is annoying any ideas would be grateful.