I have the same AImesh gear in operation, an AX86U as root for 2 XT8 nodes in star formation, stably running Merlin 3004.388.4 on former and 3004.388.2.2-gnuton1 on the latter.
With Channel Select set to Auto the root broadcasts on Ch 100 (5GHz-2 wireless backhaul on the tri-band nodes), which...