Thanks for your comment, and after a quick review for sure there are plenty of exemple with sync and/or sound drop issue. However, I spent month to review the best solution for my need and connection with HDMI was a mandatory. And it's a bit disappointingHdmi/cec/arc/earc , everyone seems to have issues and problems with connectivity, because there does not seem to be a cast in stone agreed upon unified standard globally. Every manufacturer therefore has to do there best to interpret the rules to the best of there abilities when trying to develop compatabile products.
Your problems with the stage are by no means unique. Every other soundbar irrespective of spec and cost has similar issues, just trawl this forum.
The stage is a wonderful product and well worth persevering with, I very occasionally have sound drop outs using my tv apps, had one last night so switched viewing to Netflix app onboard xbox, switched back 30 mins later, issue gone.
the probs u are having are not likely to be with the soundbar as such but a slight incompatability somewere else, switching to another suppliers products may resolve it, or make it far worse, most peeps on this forum have significant lip sync issues as an example, although luckily I have not had that. my tv when using onboard apps outputs atmos if its available, the output from the xbox is dolby+, really not noticed to much actual difference as I guess the dsp on the stage takes the signal and process it for the settings you have chosen on the soundbar.