CF-19 high pitched noise

Hey all, firstly, BIG thanks for the detail provided on the forum for the toughbook's. It's been invaluable.

However, one issue i just can't pin down, even searching here, that I've just noticed tonight. Machine is a CF-19CHB23BE.

I have a very quiet but noticeable high pitched whine coming from the front left palm rest area (near the status lights/front hotkeys). It appears to "flutter" when pressing keys / clicking the mouse or the flicker of the hdd activity light.

Already tried...

CF-19 high pitched noise

CF-19 high pitched noise