If you're experiencing erratic and inconsistent audio from your 5.1 surround sound Sonos speakers, here are some steps you can take to troubleshoot and resolve the issue:

1. Check Wireless Interference

• Sonos speakers rely on Wi-Fi to communicate, so interference from other devices (like microwaves, baby monitors, or routers) can affect audio performance.
• Switch to a less congested channel on your Wi-Fi router to reduce interference.
• Place the Sonos speakers and router farther from other wireless devices to improve signal strength.

2. Ensure Proper Speaker Placement

• Make sure the surround speakers (rear left and right) are positioned at ear level and away from walls or obstructions that might block the sound.
• Subwoofer positioning can also affect sound quality. Place it near the main speakers for better bass performance and reduce inconsistencies.

3. Check Network Connectivity

• Restart your router and Sonos speakers to reset the connection and improve stability.
• If possible, connect the Sonos soundbar or a speaker directly via Ethernet to your router, creating a SonosNet (Sonos' own wireless network), which can help reduce Wi-Fi-related issues.
• Use the Sonos app to run a network diagnosis, which can help identify network-related issues affecting your audio.

4. Adjust Audio Settings in the Sonos App

• Open the Sonos app and check the surround sound settings under the room or device settings.
• Adjust the surround audio level for rear speakers to balance the sound.
• Make sure the Trueplay tuning (Sonos’ room calibration feature) is applied. If not, re-run Trueplay calibration to optimize sound based on your room’s acoustics.

5. Check Audio Source Settings

• Ensure that the source of your content (TV, streaming service, Blu-ray player) is sending a 5.1 surround sound signal and not stereo or lower-quality audio.
• Go to your TV's or media player’s audio output settings and make sure it's set to "Dolby Digital" or "Surround Sound" to deliver the proper signal to your Sonos system.

6. Update Sonos Firmware

• Make sure that your Sonos system is running on the latest firmware. You can check for updates in the Sonos app under Settings → System → System Updates.
• Updating your system can fix bugs and improve performance.

7. Power Cycle All Devices

• Turn off your TV, Sonos speakers, and router for a few minutes, then turn them back on. Sometimes, a simple restart can resolve audio issues.

8. Factory Reset as a Last Resort

• If the problem persists, you might consider factory resetting your Sonos system, but only as a last resort. Be sure to back up or note down any customized settings before resetting, as this will wipe your configurations.

If none of these steps resolve the issue, it might be worth contacting Sonos support or seeking professional help to assess if there’s a hardware issue with your speakers.