SSID Interference between Managed FortiAPs

Hi there,

I guess I'm doing something wrong - I hope you can help me.

My topology is very simple - 40F managing FortiSwitch POE that has 7 FortiAP connected to it in Local Switching mode.

there are 3 floors, 2x831F in first floor, 2x831F in second floor, 1x831F and 2x221E on third floor.

the 831F is for each classroom, with 30 students, each has a laptop, and a phone.

I have 2 SSIDs - STAFF and STUDENTS.

yet when I look at the GUI for interfering SSID - despite the fact that the channel selection is auto, and all are controlled via the same 40F - the 831F sees the other 2 831F as interfering SSID.

but that makes no sense - they should each use it's own channel, with auto power, and auto channel selection.

how can they interfere each other ? they should support each other don't they ?

which CLI commands should I provide you ?