@Radalu 

Okay, I understand that you are experiencing very slow Wi-Fi speeds (around 10 Mbps) near your Deco Mesh satellite unit (X50), even though it is connected via Ethernet backhaul and the main Deco unit (X60) delivers full speeds. You've already checked the basics, such as firmware updates, device placement, and using the 5 GHz band, but the issue persists.

Here are some steps to help diagnose and potentially resolve the slow speed issue on your Deco Mesh network:

1. Test with Different Devices:
• Try running a speed test with another phone or laptop near the X50 to rule out device-specific issues.

2. Verify Ethernet Backhaul:
• Double-check that the Ethernet cable connecting the X50 to your main Deco is CAT5E or above and is securely connected at both ends.
• Try swapping the Ethernet cable and/or the ports used on both the X50 and main Deco to rule out a faulty cable or port.

3. Check App Settings:
• In the Deco app, go to MORE > ECO Mode and ensure that ECO Mode is disabled.
• Go to MORE > QoS and make sure QoS is disabled, or set to standard with no priority devices.
• Go to MORE > Advanced > NAT Forwarding and disable SIP ALG and UPnP.

4. Speed Test Method:
• When testing, ensure no other devices are using bandwidth on your network.
• Use https://www.speedtest.net or the Speedtest app for accurate results.

5. Firmware and Reboot:
• Ensure both Deco units are running the latest firmware.
• Reboot both the main Deco and the X50 after making any changes.

6. Test Wired Speed:
• Connect a laptop or PC directly to the X50 via Ethernet and run a speed test. If speeds are normal, the issue may be with the X50's Wi-Fi radio. If speeds are still low, it could indicate a hardware or backhaul issue.

7. Additional Troubleshooting:
• If possible, temporarily swap the locations of the X50 and X60 to see if the issue follows the unit or stays in the same location.

If you have tried all the above steps and the speed near the X50 remains much lower than expected, it is possible there is a hardware issue with the X50's Wi-Fi radio. In this case, please contact TP-Link support with the results of these troubleshooting steps for further assistance.

For more details, you can also refer to this FAQ: https://www.tp-link.com/support/faq/2429/