@voljega what a pity
But thank you for quick answers!

go game options in emulationstation menu and change by fba libretro core emulator

Une piste?
https://github.com/raspberrypi/linux/issues/1527/

Found the problem thanks to the jstest tool.
The default state of the buttons was ON because of bad wiring on the switches.
I connected the TOP pin and the LOWER pin. It is supposed to be the TOP pin and the MIDDLE pin, in contrary to what the drawing shows on the switch.
For reference, this is CORRECT connection: https://www.dropbox.com/s/qhx5fd9r0k2vbq4/IMG_20170923_0439526.jpg?dl=0
And this was the WRONG connection: https://www.dropbox.com/s/bld45u4u2mm4gfc/IMG_20170923_0440122.jpg?dl=0

@acris
Merci ! J'ai pu adapter tout ça pour ma manette du même type (il y a quelques différences au niveau des numéros de certains boutons :) et j'ai mis comme "Mapping Stop" les boutons START+B :) )

@actarus j'aurais dit un problème avec la manette mais comme tu dis que ça fonctionne parfaitement sur PC je botte en touche o0

j'ai le même probleme !!!

Just made my own arcade an came up with the same problem when I set up one the other fucks up. checked the device ID thing and the were both "ID 0079:0006"