Mac Studio Display not sleeping

[dcmaccam]

I have recently purchased a Studio Display and am currently running it with an M1 MacBook Air. All going great except one thing.
It seems to refuse to go to sleep when I put my MacBook Air to sleep. Fans are still running. Not sure if they are running all night but in the morning before touching anything I can feel the airflow out the top.

If I shut the MacBook down it goes to sleep, likewise if I leave the Mac sleeping and unplug the Thunderbolt cable the display goes to sleep.

I have two drives plugged into the studio display, one data drive and one for Time Machine (set to manual backup) Wake for Network Access is off.

Did a little exercise.

Studio Display:-

Powered everything disconnected 4 watts
" 2 SSD plugged in 6 watts
MacBook connected to the Thunderbolt cable plus 2 SSD 15-22 watts (Macbook sleeping)

MacBook awake plus 2 SSD around 30 watts

I just tried to measure this with a Hive plug (I am in the UK) not sure how accurate this is.

Anyone got any ideas ?

 

[xraydoc]

Fans are still running.

This is apparently normal behavior.

 

[dcmaccam]

For now I just unmount the two drives, put the MacBook to sleep and unplug the Thunderbolt cable for lowest power draw which puts the the fans off.