Not really sure, but it could be your cable from the TV to the soundbar.  If you have the optical cable, they’re very sensitive and weill behave that way when loose or damaged.  Try playing music through the app and if it’s the same, that would rule out the optical.

Next, I would suggest the following steps from probably easiest to hardest:

1. Make sure your OS on your phone and the app are both updated
2. Reset the app (user settings page)
3. Unplug each speaker/unit and wait 30 or so seconds before plugging back in
4. Delete and re-download the app
5. Remove the speakers, perform a “factory reset” on them (maybe one at a time) then reconnect them

Also, do you have the new app and if so, make sure all are compatible with it.  If one isn’t that could potentially cause performance issues.