Keyboard backlight coming on during M1 Mac Mini sleep

I have a Keychron K4 keyboard (Bluetooth/wired – used wired) which, until recently, I used on my old Intel Mac Mini with no problem. However, since replacing my old Mini with a new M1 version, the keyboard backlight keeps coming on during computer/monitor/keyboard sleep. All settings on the M1 match those on my Intel Mini, so what could be waking the keyboard but not the monitor?