I’ve had this same issue with a different laptop. On my machine, any change in WiFi network or Bluetooth device availability would cause the laptop to spin up, prevent sleep, and drain battery. One trick is to turn off connected standby and switch to “disconnected modern standby”. That disables the WiFi and Bluetooth chips during standby, which should solve your issues. The only downside I’m aware of is that the machine will take a few seconds upon awakening to reconnect to WiFi and Bluetooth peripherals.

Alternatively, you can disable connected/modern standby altogether and revert to traditional S3 sleep. You lose that instant-on tablet effect, but it should fix the excess battery drain too.