I have a transparent model for a game/interactive I created, and the engine seems to have a problem with rendering an alpha on all of the faces. I have tried enabling and disabling two-sided, and it looks like it only succeeds in moving the problem around.
Here it is with two sided:
Here it is without:
Either way, the problem occurs at the transverse midline–some of the faces are invisible.
I don’t know whether normals would be to blame–I fixed anything that looked flipped long ago and it still looks okay in edit mode.
Under Edit>Texture Face, I have enabled Tex and Alpha, and Twoside in the first example.
Let me know if there is any other info I can provide.