So this is the original model:
But when I import it this happens:
I looked with back culling in blender and it couldn’t find it, I inverted it anyway, I used bulk imports reversed normal check box. Nothing works! It just keeps inverting those triangled shapes. I tried moving the faces to see for duplicated ones but there aren’t any. I made it flat and smooth shade and it also didn’t work.
Please help me!
Did you try enabling the Double Sided option in studio?
hello, in the blender faces button you can click and open it, inside you will see an option called see orientation of faces, you have to enable it and so you can see your normals are inverted.
if your normals are not inverted it is because there must be an inverted face on top of another face that is not inverted, you have to redo your model from 0 and it is time more carefully or simply remove the faces one by one and check if this is not inverted.
Yes I did but it does nothing 
I said I already inverted and checked for duplicates there aren’t any.
Found a solution:Issue with faces randomly disappearing when uploaded [FBX file] - #5 by impjelly Thanks for trying to help though.
You can also try simply applying transform to the mesh. Worked for me for a similar issue exporting fbx
