I answer to myself (and this is very sad, I hoped that at least someone had written something, even as “moral help”)… I solved my problem.
I had basically been signed up for the xbox insider program for a couple of years, this allowed me to get updates before others, updates that I couldn’t skip. After unsubscribing from the program, I then proceeded to reset the firmware of the elite controller (for the record, it didn’t let me do the same procedure on the other pads) and that was enough, I hope I can be of help to others 
If you have any questions, just ask, I’ll try to help you as much as I can ^^