Ok, so I installed the latest update of the BIOS again (1.7.0), ran the uninstall from the Killer website again, and this time it's been 2 days and the fan seems OK! Let's hope it's for good!
I have the same problem with my laptop Dell XPS 13 9380. I tried to fix it as your solution but it's quite in few minutes only.
How can I fix it or I will use Dell XPS 13 9380 to dry my hair?
For some reason, the fan stops completely when I open the task manager to see what's running. It's as if it gets scared or something (like the double-slit experiment in Physics!) 👨🎓
I do this once every time I restart the PC and I'm Ok for now...