Could you provide details about the storing conditions of the device? For example, is it not enclosed or covered by any metallic surfaces, which could attenuate or reflect radio signals?
Could you try to login to the router's WebUI, navigate to Network -> Firewall -> General settings, enable Software flow offloading and check if that has any impact on data speeds?
As for WiFi MAC override, there is indeed an issue with changing WiFi WAN interface's MAC, as the address is saved in the wrong configuration file, however, you can try changing the address via CLI/SSH. The commands should look similar:
- uci set wireless.@wifi-iface.macaddr='<MAC_address>'
- uci commit
Replace <MAC_address> with address of your needs.
Alternatively, you can edit the configuration file with a text editor, for example:
and add the following option under client's interface settings by pressing i letter to start editing:
- option macaddr '<MAC_address>'
Exit editing by pressing ESC, enter :wq and press Enter, then in the terminal execute reload_config command.
Also, I would like you to attach a troubleshoot file to your question. Please, replicate your device configuration used for your testing, then access router's WebUI, go to System -> Administration -> Troubleshoot section and download troubleshoot file from there. The logs in the file might provide more insight into the issue.