M1 5GHz switches to 20MHz bandwidth randomly

Zyxel M1 randomly switches from 80MHz to 20MHz band for the 5GHz network. This is temporarily solved by rebooting but happens again after some hours, or a couple days maximum.

I have 3 M1s connected via Ethernet backhaul, one base station and two satellites, one for each floor.

The issue happens consistently, and exclusively, on the satellite in the middle floor. I don't think this can be a compatibility problem since all the devices connect to all the M1s depending on the location, and there are no static devices on this floor. I already tried factory resetting the satellite.

This is the situation seen in WiFiman

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