If you are using firmware 386.1, that one is using ASUS's AI MESH 2.0, new code base. So they most likely still are sorting bugs and it is closed source, i.e. it is out of the control of the devs behind ASUS WRT Merlin.Strange. I have a situation where I have an AC88U as master en one AC68U as Aimesh Node + another AC68U as simple AP.
I sit at about 2 m from the AC88U, 4 meter from the AC68U Aimesh Node (one extra wall) and 10 m from the AC68U AP (3 to 4 walls inbetween).
I noticed I do not have WIFI on one of my devices (iphone), when I connect I get a connetion error. Then suddenly it connects to the very weak signal of the router that is the furthest away.
Why are the Aimesh router and node refusing this connection to leave me at a weak signal?
I also seem to experience drop-outs on the node.
I have tried all kinds of stuff but no success so far. A power cycle helps but this should not be needed if I read the above positive feedback of some.