You may want to take a look at this thread.
http://forum.mikrotik.com/t/extremely-poor-wifi-of-macbook-pro-m1-pro/164406/1
User reported Wifi issues on AX2 (same wifi as AX3) using ROS 7.7 yet the problem turned out to be related to Macbook.
Other test device, problem went away.
So once again my suggestion to ditch Apple 
In all seriousness, to further pinpoint this problem, do you have the option to use another device for your testing ?