We've tried a few things but it hasn't really helped.

When it goes offline I get the following error on the Flint 3:

    # dmesg | grep -i '54:EF:44:5C:BC:B1' | grep kicked
    [3356208.016938] wlan: [0:I:ANY] [INACT] vap-0(wlan0): [54:ef:44:5c:bc:b1]station kicked out due to excessive retries associd 4 (from target) reason 1
    [3363271.980807] wlan: [0:I:ANY] [INACT] vap-0(wlan0): [54:ef:44:5c:bc:b1]station kicked out due to excessive retries associd 4 (from target) reason 1

I'm pretty sure it is dodgy firmware on the Doorbell, but I couldn't get any actual support from Aqara on this, so I thought there might be some workaround I could do on the AP.