Bug My AK-47 model has 2 random faces missing

I believe that it is an issue with either importation or the editor given that the model appears to be completely fine, but please let me know if I should move this to the blender forum. My issue is that I have a model of a gun that appears completely fine within blender, but when I import it, it either has the back and right faces missing, or the two side faces missing or transparent maybe. I can find no issue within blender, but the model preview within unity shows the handle has 2 faces missing for seemingly no reason. Here are the pictures of my issue. Also it was imported with .fbx format if that helps in any way.


Also, the faces missing varies based on how my character is rotated so I have no idea why that happens either

 

Your model's normals are inverted.

 

I'd eager the normals are just flipped around. Top corner of the 3d view, with all the spheres, the dropdown has options to view the direction of face normals.

I believe the shortcut to recalculate normals is CRTL-N, so just select all your verts and hit that shortcut.

You often don't see this in Blender as it doesn't have backface culling on by default.

 

Thanks for your help, recalculating the normals solved my issue