Can you please show all wireless settings (including security, password is not relevant)? At what speed is the client connected? Is there a line of sight while testing? How are you testing, iperf3 (preferably)?
I prefer to avoid using auto: select a channel that is least used. And use WPA2 AES only.
For wireless (turn on advanced mode): wireless protocol: 802.11, set country code to meet regulations, distance indoor.
There is a lot more to tweak, but these settings should give you a lot better performance!