One thing you could try is reinstalling BIOS 49 using the Recovery Method (see here: Intel NUC BIOS Recovery Update Instructions; I recommend using the jumper method). If you try this, let us know if the issue resolves or continues to occur.
Thank you for the suggestion. I performed the recovery method with the jumper method, but the problem still persists. It seems to be tied to WoL, as waking the NUC with the power button activates the fan as expected.
Ok, Intel Customer Support will need to report this to the development team...
Thank you for contacting the Intel community.
This is an issue that it was already fixed with the BIOS version 0048 as you can see here:
Can you try to roll back to bios version 0048 using the recovery method and then upgrade to version 0049?
Please let me know how it goes.
I am currently on a business trip and can only
try your proposed fix in two weeks, my apologies.
In the meantime, I upgraded the BIOS to the latest
version 0050, but the problem with the fan persists.
Thank you for the information, please let me know how it goes if you can roll back to BIOS version 0048 and then upgrade to version 0048 and then to 0050.