Mame 2015 select buton opening menu

Hello, i’m configuring killer instinct to play on my lakka pc, but the only core that i could play it was mame2015 (tried a lot of versions). But the only problem is that every time i press the coin button (select/ button 8), it opens the mame menu (TAB on kb). I’ve searched a lot but couldn’t find the solution. Has anyone manage to solve this? Thanks