Marmoset slight issue

[Roninfang]

okay i have a weird issue with my marmoset tool bag for the pc

was working on a paid 3d model for a game studio

3d model looks fine on render in maya, 3dmax and blender
but when i test in marmoset...some of the faces at the back are not showing

already turned off back face curl in marmoset...so not sure what is wrong

cant post the 3d art, since the studio dont post/add it to my portforlio yet

" though don't do it right away, cause we need to copyright stuff"

anyways i hope it wont be a major issue when they load the 3d model in the game engine

[Sir Apple]

It could be flipped normals or quads, marmoset is iffy with that.