Hello James, sorry for the delay (and happy new year btw).
No, I connected this cable to the motherboard to let met synchronise the whole system whenever I want to do it. This is working so no problem with that.
Yes, all other fans work. As you can see in this short video (we can see the back panel fan in the background) :
Oh, if the problem seems to be mechanical and not due to a bad configuration, that could be great, thanks !
Here the video :
As you can see, all leds stopped with a "wrong" configuration. Is that due to the problematic fan ? (in the video, I connected it to the first port). If you need more information (more configuration for example), let me know. I'll try to do a more detailed one.
Thank you.