Problem with transparency of an object

Hi ! If I'm here, it's because I hope someone could help me with a problem I met with a cutout shader. I'm currently working on a project where our assets use vertex color, but just one object isn't working correctly : a part of the object where there is an alpha doesn't appear. There is the wireframe, but not the faces with texture.. and it happens only with the vertex color's shader. Anyone know why ? I tried many thing : modelling once again the object, bake again vertex color, made another alpha channel with photoshop, checking the texture... I don't know what should I try now.. Any idea ?