Shutdown / Poweroff on Windows 10 with Up board fails randomly ... ?

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Hello

one more question about the UP board and Windows 10 ... after a shutdown of Windows 10 normally the Up board takes about 10-30 seconds after Windows has finished the shutdown and then the blue LED on the Upboard goes off, the fan stops and the 3.3V falls, the 5V line input still stays active until the external power of 5V is switched off. Up to here its the normal behaviour ...

But sometimes the Upboard finishes the Windows Shutdown, the fan continues running and the 3.3V stays active ... for hours ... and hours ...

What is happening that the power off after the shut down sometimes isn't working correctly ?

In these cases what I do normally is, I switch the external Power off but if I do not the fan continues running for nothing for hours ...

Please can somebody tell me why this happens sometimes and sometimes not ?

It seems not like Windows would not finish because the windows shutdown shows no more activity and the HDMI screen goes off ...

For information the blue LED stays on and the LED of Ethernet port is still blinking too ... (because the external Ethernet Switch is still communicating with other devices and the ethernet port of the up board still sees all broadcast messages ... ?)

Personally I would have imagined the Ethernet Stack of the upboard should have been stopped after a shutdown of the upboard ?

Best regards

Martin