Recently, the Paramount + App has started only outputting Stereo sound on the XG1v4. Does not matter if the box is in Expert Mode or Auto Detect. The receiver reports either Multichannel PCM 5.1 or Dolby Digital Plus but only the left and right channels are receiving audio. 

The issue is limited to Youtube and Paramount+ on the X1 Box. All other built in apps such as Netflix , Peacock, HBO Max, or Disney+ all properly output 5.1 surround. 

As a test, I played the same Youtube and Paramount+ content on my smart TV app and AppleTV and got 5.1 no problem.