One button of my pad does not work in Mame

[Fraaalesi]

Hi all,

in mame, I have the 3rd button that does not work.
I think I have tested everything to make it work and this post is my last hope before reinstalling Recalbox. Do you have any idea ?
It works in all emulators but mame. I tried to configure it also in Retroarch menu inside mame: it was recognized during the config but after that it still does not work in game.
I'm willing to delete whatever config file you suggest. Please please please, any idea is welcome

Problem is still there after 18.02.09 update. I have 2 wireless X360 pad and only the first connected has the problem. This is NOT a hardware problem. I think I have modified something one day from retroarch menu inside mame but cannot remember what.

[Fraaalesi]

So I feel like I will have to wipe clean/reinstall my sdcard... No solution ? Anyone ?!