ORBI853 wired backhaul speed stuck at 400M, wireless backhaul is normal

My ORBI 853 device is a product from China. I used nmrpflash to downgrade it to the lowest version, 3.1.5.23, enabled telnet, then navigated to the "bin" directory, executed "burnsku 0×0002," rebooted, and then used nmrpflash to flash it to version 7.2.7.15. During the flashing process, running the command .\nmrpflash.exe -i net19 -a 192.168.1.1 -f 2.chk resulted in a timeout error. Adding the parameter "-AU" (likely for Australia) resolved the issue, although there was a minor error I’ve forgotten, which I ignored. The device booted successfully. After reconfiguring and enabling AP mode, the wireless backhaul between the main router and satellite worked fine, achieving speeds close to 1000 Mbps. However, with wired backhaul, the main router’s Wi-Fi speed was normal, but the satellite’s wireless speed tests did not exceed 400 Mbps.

I’ve already checked and ruled out the following potential issues:

1. Replaced the Ethernet cables multiple times.
2. Verified that both the main router and satellite LAN ports support gigabit speeds.
3. Tested both AP mode and router mode, as well as direct connection to the optical modem; the results were the same.
4. Attempted flashing without using nmrpflash.exe and without the "-AU" parameter, instead upgrading via the web interface, but the issue persisted.
5. Upgraded to the latest firmware, but the problem remains.
6. The web interface shows the wired connection as "good."
7. Connected devices show a 5G connection, but the speed test does not exceed 400 Mbps.

Currently, it seems that after inserting the wired connection, the 5G transmission frequency decreases, or the MIMO is limited to 1×1 with 80 MHz.