Router: RT-AC86U in Ai-Mesh mode, firmware 3.0.384.19; in my house;
Node: RT-AC68U, firmware 3.0.384.19; in external wooden building approx 10m away;
A/C unit is in the wooden building approx 6 metres from the AC68U unit with a direct line of sight.
Wifi strength is very good in the building...