Diagnosis
Wireless interference is disrupting the signal between the soundbar and the rear satellite speakers.
How to Fix It
Move your Wi-Fi router or any other major wireless device (like a cordless phone base) at least 3 feet away from the soundbar and the rear speaker receivers. 5GHz router bands cause less interference than 2.4GHz.
If That Didn't Work
The issue might be with the speaker connections. Power everything down. Remove the plastic covers from the speaker terminals on the rear speakers and the wireless transmitter unit. Ensure the bare wire is firmly screwed into the correct positive/negative terminals.
Heads Up
Do not place the wireless transmitter unit inside a closed cabinet. It needs a clear line of sight to the rear speakers for a stable signal.